music21.meter.base

This module defines the TimeSignature object, as well as component objects for defining nested metrical structures, MeterTerminal and MeterSequence objects.

TimeSignature

class music21.meter.base.TimeSignature(value: str = '4/4', divisions=None, **keywords)

The TimeSignature object represents time signatures in musical scores (4/4, 3/8, 2/4+5/16, Cut, etc.).

TimeSignatures should be present in the first Measure of each Part that they apply to. Alternatively you can put the time signature at the front of a Part or at the beginning of a Score, and they will work within music21, but they won’t necessarily display properly in MusicXML, Lilypond, etc. So best is to create structures where the TimeSignature goes in the first Measure of the score, as below:

>>> s = stream.Score()
>>> p = stream.Part()
>>> m1 = stream.Measure()
>>> ts = meter.TimeSignature('3/4')
>>> m1.insert(0, ts)
>>> m1.insert(0, note.Note('C#3', type='half'))
>>> n = note.Note('D3', type='quarter')
>>> m1.insert(1.0, n)
>>> m1.number = 1
>>> p.insert(0, m1)
>>> s.insert(0, p)
>>> s.show('t')
{0.0} <music21.stream.Part ...>
    {0.0} <music21.stream.Measure 1 offset=0.0>
        {0.0} <music21.meter.TimeSignature 3/4>
        {0.0} <music21.note.Note C#>
        {1.0} <music21.note.Note D>

Basic operations on a TimeSignature object are designed to be very simple.

>>> ts.ratioString
'3/4'

>>> ts.numerator
3

>>> ts.beatCount
3

>>> ts.beatCountName
'Triple'

>>> ts.beatDuration.quarterLength
1.0

As an alternative to putting a TimeSignature in a Stream at a specific position (offset), it can be assigned to a special property in Measure that positions the TimeSignature at the start of a Measure. Notice that when we show() the Measure (or if we iterate through it), the TimeSignature appears as if it’s in the measure itself:

>>> m2 = stream.Measure()
>>> m2.number = 2
>>> ts2 = meter.TimeSignature('2/4')
>>> m2.timeSignature = ts2
>>> m2.append(note.Note('E3', type='half'))
>>> p.append(m2)
>>> s.show('text')
{0.0} <music21.stream.Part ...>
    {0.0} <music21.stream.Measure 1 offset=0.0>
        {0.0} <music21.meter.TimeSignature 3/4>
        {0.0} <music21.note.Note C#>
        {1.0} <music21.note.Note D>
    {2.0} <music21.stream.Measure 2 offset=2.0>
        {0.0} <music21.meter.TimeSignature 2/4>
        {0.0} <music21.note.Note E>

Once a Note has a local TimeSignature, a Note can get its beat position and other meter-specific parameters. Remember n, our quarter note at offset 2.0 of m1, a 3/4 measure? Let’s get its beat:

>>> n.beat
2.0

This feature is more useful if there are more beats:

>>> m3 = stream.Measure()
>>> m3.timeSignature = meter.TimeSignature('3/4')
>>> eighth = note.Note(type='eighth')
>>> m3.repeatAppend(eighth, 6)
>>> [thisNote.beatStr for thisNote in m3.notes]
['1', '1 1/2', '2', '2 1/2', '3', '3 1/2']

Now lets change its measure’s TimeSignature and see what happens:

>>> sixEight = meter.TimeSignature('6/8')
>>> m3.timeSignature = sixEight
>>> [thisNote.beatStr for thisNote in m3.notes]
['1', '1 1/3', '1 2/3', '2', '2 1/3', '2 2/3']

TimeSignature(‘6/8’) defaults to fast 6/8:

>>> sixEight.beatCount
2

>>> sixEight.beatDuration.quarterLength
1.5

>>> sixEight.beatDivisionCountName
'Compound'

Let’s make it slow 6/8 instead:

>>> sixEight.beatCount = 6
>>> sixEight.beatDuration.quarterLength
0.5

>>> sixEight.beatDivisionCountName
'Simple'

Now let’s look at the beatStr for each of the notes in m3:

>>> [thisNote.beatStr for thisNote in m3.notes]
['1', '2', '3', '4', '5', '6']

As of v7., 3/8 also defaults to fast 3/8, that is, one beat:

>>> meter.TimeSignature('3/8').beatCount
1

TimeSignatures can also use symbols instead of numbers

>>> tsCommon = meter.TimeSignature('c')  # or common
>>> tsCommon.beatCount
4
>>> tsCommon.denominator
4

>>> tsCommon.symbol
'common'

>>> tsCut = meter.TimeSignature('cut')
>>> tsCut.beatCount
2
>>> tsCut.denominator
2

>>> tsCut.symbol
'cut'

For other time signatures, the symbol is ‘’ (not set) or ‘normal’

>>> sixEight.symbol
''

For complete details on using this object, see User’s Guide Chapter 14: Time Signatures and User’s Guide Chapter 55: Advanced Meter and

That’s it for the simple aspects of TimeSignature objects. You know enough to get started now!

Under the hood, they’re extremely powerful. For musicians, TimeSignatures do (at least) three different things:

  • They define where the beats in the measure are and how many there are.

  • They indicate how the notes should be beamed

  • They give a sense of how much accent or weight each note gets, which also defines which are important notes and which might be ornaments.

These three aspects of TimeSignatures are controlled by the beatSequence, beamSequence, and accentSequence properties of the TimeSignature. Each of them is an independent MeterSequence element which might have nested properties (e.g., an 11/16 meter might be beamed as {1/4+1/4+{1/8+1/16}}), so if you want to change how beats are calculated or beams are generated you’ll want to learn more about meter.MeterSequence objects.

There’s a fourth MeterSequence object inside a TimeSignature, and that is the displaySequence. That determines how the TimeSignature should actually look on paper. Normally this MeterSequence is pretty simple. In ‘4/4’ it’s usually just ‘4/4’. But if you have the ‘11/16’ time above, you may want to have it displayed as ‘2/4+3/16’ or ‘11/16 (2/4+3/16)’. Or you might want the written TimeSignature to contradict what the notes imply. All this can be done with .displaySequence.

Equality

For two time signatures to be considered equal, they have the same name and internal structure.

The name is tested by the symbol. This helps distinguish between ‘Cut’ and ‘2/2’, for example.

>>> tsCut = meter.TimeSignature('Cut')
>>> ts22 = meter.TimeSignature('2/2')
>>> tsCut == ts22
False

The internal structure is currently tested simply by the beatCount and ratioString attributes.

The check of beatCount helps to distinguish the ‘fast’ (2-beat) from ‘slow’ (6-beat) versions of 6/8, for example.

>>> fast68 = meter.TimeSignature('fast 6/8')
>>> slow68 = meter.TimeSignature('slow 6/8')
>>> fast68 == slow68
False

Complementing this, ratioString provides a check of the internal divsions such that ‘2/8+3/8’ is different from ‘3/8+2/8’, for example, despite the fact that they could both be written as ‘5/8’.

>>> ts2n3 = meter.TimeSignature('2/8+3/8')
>>> ts3n2 = meter.TimeSignature('3/8+2/8')
>>> ts2n3 == ts3n2
False

For a less restrictive test of this, see ratioEqual() which returns True for all cases of ‘5/8’.

>>> ts2n3.ratioEqual(ts3n2)
True

Yes, equality is ever True:

>>> one44 = meter.TimeSignature('4/4')
>>> another44 = meter.TimeSignature()  # '4/4' by default
>>> one44 == another44
True

TimeSignature bases

TimeSignature read-only properties

TimeSignature.beatCountName

Return the beat count name, or the name given for the number of beat units. For example, 2/4 is duple; 9/4 is triple.

>>> ts = meter.TimeSignature('3/4')
>>> ts.beatCountName
'Triple'

>>> ts = meter.TimeSignature('6/8')
>>> ts.beatCountName
'Duple'
TimeSignature.beatDivisionCount

Return the count of background beat units found within one beat, or the number of subdivisions in the beat unit in this TimeSignature.

>>> ts = meter.TimeSignature('3/4')
>>> ts.beatDivisionCount
2

>>> ts = meter.TimeSignature('6/8')
>>> ts.beatDivisionCount
3

>>> ts = meter.TimeSignature('15/8')
>>> ts.beatDivisionCount
3

>>> ts = meter.TimeSignature('3/8')
>>> ts.beatDivisionCount
1

>>> ts = meter.TimeSignature('13/8', 13)
>>> ts.beatDivisionCount
1

  • Changed in v7: return 1 instead of a TimeSignatureException.

TimeSignature.beatDivisionCountName

Return the beat count name, or the name given for the number of beat units. For example, 2/4 is duple; 9/4 is triple.

>>> ts = meter.TimeSignature('3/4')
>>> ts.beatDivisionCountName
'Simple'

>>> ts = meter.TimeSignature('6/8')
>>> ts.beatDivisionCountName
'Compound'

Rare cases of 5-beat divisions return ‘Other’, like this 10/8 divided into 5/8 + 5/8 with no further subdivisions:

>>> ts = meter.TimeSignature('10/8')
>>> ts.beatSequence.partition(2)
>>> ts.beatSequence
<music21.meter.core.MeterSequence {5/8+5/8}>
>>> for i, mt in enumerate(ts.beatSequence):
...     ts.beatSequence[i] = mt.subdivideByCount(5)
>>> ts.beatSequence
<music21.meter.core.MeterSequence {{1/8+1/8+1/8+1/8+1/8}+{1/8+1/8+1/8+1/8+1/8}}>
>>> ts.beatDivisionCountName
'Other'
TimeSignature.beatDivisionDurations

Return the beat division, or the durations that make up one beat, as a list of Duration objects, if and only if the TimeSignature has a uniform beat division for all beats.

>>> ts = meter.TimeSignature('3/4')
>>> ts.beatDivisionDurations
[<music21.duration.Duration 0.5>,
 <music21.duration.Duration 0.5>]

>>> ts = meter.TimeSignature('6/8')
>>> ts.beatDivisionDurations
[<music21.duration.Duration 0.5>,
 <music21.duration.Duration 0.5>,
 <music21.duration.Duration 0.5>]

Value returned of non-uniform beat divisions will change at any time after v7.1 to avoid raising an exception.

TimeSignature.beatDuration

Return a Duration object equal to the beat unit of this Time Signature, if and only if this TimeSignature has a uniform beat unit.

Otherwise, raises an exception in v7.1 but will change to returning NaN soon fasterwards.

>>> ts = meter.TimeSignature('3/4')
>>> ts.beatDuration
<music21.duration.Duration 1.0>
>>> ts = meter.TimeSignature('6/8')
>>> ts.beatDuration
<music21.duration.Duration 1.5>

>>> ts = meter.TimeSignature('7/8')
>>> ts.beatDuration
<music21.duration.Duration 0.5>

>>> ts = meter.TimeSignature('3/8')
>>> ts.beatDuration
<music21.duration.Duration 1.5>
>>> ts.beatCount = 3
>>> ts.beatDuration
<music21.duration.Duration 0.5>

Cannot do this because of asymmetry

>>> ts = meter.TimeSignature('2/4+3/16')
>>> ts.beatDuration
Traceback (most recent call last):
music21.exceptions21.TimeSignatureException: non-uniform beat unit: [2.0, 0.75]

  • Changed in v7: return NaN rather than raising Exception in property.

TimeSignature.beatLengthToQuarterLengthRatio

Returns 4.0 / denominator. Might seem a bit silly but used often.

>>> a = meter.TimeSignature('3/2')
>>> a.beatLengthToQuarterLengthRatio
2.0
TimeSignature.beatSubDivisionDurations

Return a subdivision of the beat division, or a list of Duration objects representing each beat division divided by two.

>>> ts = meter.TimeSignature('3/4')
>>> ts.beatSubDivisionDurations
[<music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>,
 <music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>]

>>> ts = meter.TimeSignature('6/8')
>>> ts.beatSubDivisionDurations
[<music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>,
 <music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>,
 <music21.duration.Duration 0.25>, <music21.duration.Duration 0.25>]
TimeSignature.classification

Return the classification of this TimeSignature, such as Simple Triple or Compound Quadruple.

>>> ts = meter.TimeSignature('3/4')
>>> ts.classification
'Simple Triple'
>>> ts = meter.TimeSignature('6/8')
>>> ts.classification
'Compound Duple'
>>> ts = meter.TimeSignature('4/32')
>>> ts.classification
'Simple Quadruple'
TimeSignature.quarterLengthToBeatLengthRatio

Returns denominator/4.0.

Read-only properties inherited from Music21Object:

Read-only properties inherited from ProtoM21Object:

TimeSignature read/write properties

TimeSignature.barDuration

Return a Duration object equal to the total length of this TimeSignature.

>>> ts = meter.TimeSignature('5/16')
>>> ts.barDuration
<music21.duration.Duration 1.25>

>>> ts2 = meter.TimeSignature('3/8')
>>> d = ts2.barDuration
>>> d.type
'quarter'
>>> d.dots
1
>>> d.quarterLength
1.5

This can be overridden to create different representations or to contradict the meter.

>>> d2 = duration.Duration(1.75)
>>> ts2.barDuration = d2
>>> ts2.barDuration
<music21.duration.Duration 1.75>

An uninitialized TimeSignature returns 4.0 for 4/4

>>> meter.TimeSignature().barDuration
<music21.duration.Duration 4.0>
TimeSignature.beatCount

Return or set the count of beat units, or the number of beats in this TimeSignature.

When setting beat units, one level of sub-partitions is automatically defined. Users can specify beat count values as integers or as lists of durations. For more precise configuration of the beat MeterSequence, manipulate the .beatSequence attribute directly.

>>> ts = meter.TimeSignature('3/4')
>>> ts.beatCount
3
>>> ts.beatDuration.quarterLength
1.0
>>> ts.beatCount = [1, 1, 1, 1, 1, 1]
>>> ts.beatCount
6
>>> ts.beatDuration.quarterLength
0.5

Setting a beat-count directly is a simple, high-level way to configure the beatSequence. Note that his may not configure lower level partitions correctly, and will raise an error if the provided beat count is not supported by the overall duration of the .beatSequence MeterSequence.

>>> ts = meter.TimeSignature('6/8')
>>> ts.beatCount  # default is 2 beats
2
>>> ts.beatSequence
<music21.meter.core.MeterSequence {{1/8+1/8+1/8}+{1/8+1/8+1/8}}>
>>> ts.beatDivisionCountName
'Compound'
>>> ts.beatCount = 6
>>> ts.beatSequence
<music21.meter.core.MeterSequence
    {{1/16+1/16}+{1/16+1/16}+{1/16+1/16}+{1/16+1/16}+{1/16+1/16}+{1/16+1/16}}>
>>> ts.beatDivisionCountName
'Simple'
>>> ts.beatCount = 123
Traceback (most recent call last):
music21.exceptions21.TimeSignatureException: cannot partition beat with provided value: 123

>>> ts = meter.TimeSignature('3/4')
>>> ts.beatCount = 6
>>> ts.beatDuration.quarterLength
0.5
TimeSignature.denominator

Return the denominator of the TimeSignature as a number or set it.

(for complex TimeSignatures, note that this comes from the .beamSequence of the TimeSignature)

>>> ts = meter.TimeSignature('3/4')
>>> ts.denominator
4
>>> ts.denominator = 8
>>> ts.ratioString
'3/8'

In this following case, the TimeSignature is silently being converted to 9/8 to get a single digit denominator:

>>> ts = meter.TimeSignature('2/4+5/8')
>>> ts.denominator
8
TimeSignature.numerator

Return the numerator of the TimeSignature as a number.

Can set the numerator for a simple TimeSignature. To set the numerator of a complex TimeSignature, change beatCount.

(for complex TimeSignatures, note that this comes from the .beamSequence of the TimeSignature)

>>> ts = meter.TimeSignature('3/4')
>>> ts.numerator
3
>>> ts.numerator = 5
>>> ts
<music21.meter.TimeSignature 5/4>

In this case, the TimeSignature is silently being converted to 9/8 to get a single digit numerator:

>>> ts = meter.TimeSignature('2/4+5/8')
>>> ts.numerator
9

Setting a summed time signature’s numerator will change to a simple time signature

>>> ts.numerator = 11
>>> ts
<music21.meter.TimeSignature 11/8>
TimeSignature.ratioString

Returns or sets a simple string representing the time signature ratio.

>>> threeFour = meter.TimeSignature('3/4')
>>> threeFour.ratioString
'3/4'

It can also be set to load a new one, but ‘.load()’ is better:

>>> threeFour.ratioString = '5/8'  # now this variable name is dumb!
>>> threeFour.numerator
5
>>> threeFour.denominator
8

>>> complexTime = meter.TimeSignature('2/4+3/8')
>>> complexTime.ratioString
'2/4+3/8'

For advanced users, getting the ratioString is the equivalent of partitionDisplay on the displaySequence:

>>> complexTime.displaySequence.partitionDisplay
'2/4+3/8'
TimeSignature.summedNumerator

Read/write properties inherited from Music21Object:

TimeSignature methods

TimeSignature.averageBeatStrength(streamIn, notesOnly=True)

returns a float of the average beat strength of all objects (or if notesOnly is True [default] only the notes) in the Stream specified as streamIn.

>>> s = converter.parse('C4 D4 E8 F8', format='tinyNotation').flatten().notes.stream()
>>> sixEight = meter.TimeSignature('6/8')
>>> sixEight.averageBeatStrength(s)
0.4375
>>> threeFour = meter.TimeSignature('3/4')
>>> threeFour.averageBeatStrength(s)
0.5625

If notesOnly is False then test objects will give added weight to the beginning of the measure:

>>> sixEight.averageBeatStrength(s, notesOnly=False)
0.4375
>>> s.insert(0.0, clef.TrebleClef())
>>> s.insert(0.0, clef.BassClef())
>>> sixEight.averageBeatStrength(s, notesOnly=False)
0.625
TimeSignature.getAccent(qLenPos: OffsetQL) → bool

Return True or False if the qLenPos is at the start of an accent division.

>>> a = meter.TimeSignature('3/4', 3)
>>> a.accentSequence.partition([2, 1])
>>> a.accentSequence
<music21.meter.core.MeterSequence {2/4+1/4}>
>>> a.getAccent(0.0)
True
>>> a.getAccent(1.0)
False
>>> a.getAccent(2.0)
True
TimeSignature.getAccentWeight(qLenPos, level=0, forcePositionMatch=False, permitMeterModulus=False)

Given a qLenPos, return an accent level. In general, accents are assumed to define only a first-level weight.

If forcePositionMatch is True, an accent will only be returned if the provided qLenPos is a near exact match to the provided quarter length. Otherwise, half of the minimum quarter length will be provided.

If permitMeterModulus is True, quarter length positions greater than the duration of the Meter will be accepted as the modulus of the total meter duration.

>>> ts1 = meter.TimeSignature('3/4')
>>> [ts1.getAccentWeight(x) for x in range(3)]
[1.0, 0.5, 0.5]

Calling getAccentWeight on durations beyond the score returns an error:

>>> [ts1.getAccentWeight(x) for x in range(6)]
Traceback (most recent call last):
music21.exceptions21.MeterException: cannot access from qLenPos 3.0
    where total duration is 3.0

The error is removed if permitMeterModulus is employed:

>>> [ts1.getAccentWeight(x, permitMeterModulus=True) for x in range(6)]
[1.0, 0.5, 0.5, 1.0, 0.5, 0.5]
TimeSignature.getBeams(srcList: stream.Stream | t.Sequence[base.Music21Object], measureStartOffset: OffsetQL = 0.0) → list[beam.Beams | None]

Given a qLen position and an iterable of Music21Objects, return a list of Beams objects.

The iterable can be a list (of elements) or a Stream (preferably flat) or a StreamIterator from which Durations and information about note vs. rest will be extracted.

Objects are assumed to be adjoining; offsets are not used, except for measureStartOffset()

Must process a list/Stream at time, because we cannot tell when a beam ends unless we see the context of adjoining durations.

>>> a = meter.TimeSignature('2/4', 2)
>>> a.beamSequence[0] = a.beamSequence[0].subdivide(2)
>>> a.beamSequence[1] = a.beamSequence[1].subdivide(2)
>>> a.beamSequence
<music21.meter.core.MeterSequence {{1/8+1/8}+{1/8+1/8}}>
>>> b = [note.Note(type='16th') for _ in range(8)]
>>> c = a.getBeams(b)
>>> len(c) == len(b)
True
>>> print(c)
[<music21.beam.Beams <music21.beam.Beam 1/start>/<music21.beam.Beam 2/start>>,
 <music21.beam.Beams <music21.beam.Beam 1/continue>/<music21.beam.Beam 2/stop>>,
 <music21.beam.Beams <music21.beam.Beam 1/continue>/<music21.beam.Beam 2/start>>,
 <music21.beam.Beams <music21.beam.Beam 1/stop>/<music21.beam.Beam 2/stop>>,
 <music21.beam.Beams <music21.beam.Beam 1/start>/<music21.beam.Beam 2/start>>,
 <music21.beam.Beams <music21.beam.Beam 1/continue>/<music21.beam.Beam 2/stop>>,
 <music21.beam.Beams <music21.beam.Beam 1/continue>/<music21.beam.Beam 2/start>>,
 <music21.beam.Beams <music21.beam.Beam 1/stop>/<music21.beam.Beam 2/stop>>]

>>> a = meter.TimeSignature('6/8')
>>> b = [note.Note(type='eighth') for _ in range(6)]
>>> c = a.getBeams(b)
>>> print(c)
[<music21.beam.Beams <music21.beam.Beam 1/start>>,
 <music21.beam.Beams <music21.beam.Beam 1/continue>>,
 <music21.beam.Beams <music21.beam.Beam 1/stop>>,
 <music21.beam.Beams <music21.beam.Beam 1/start>>,
 <music21.beam.Beams <music21.beam.Beam 1/continue>>,
 <music21.beam.Beams <music21.beam.Beam 1/stop>>]

>>> fourFour = meter.TimeSignature('4/4')
>>> nList = [note.Note(type=d) for d in ('eighth', 'quarter', 'eighth',
...                                      'eighth', 'quarter', 'eighth')]
>>> beamList = fourFour.getBeams(nList)
>>> print(beamList)
[None, None, None, None, None, None]

Pickup measure support included by taking in an additional measureStartOffset argument.

>>> twoTwo = meter.TimeSignature('2/2')
>>> nList = [note.Note(type='eighth') for _ in range(5)]
>>> beamList = twoTwo.getBeams(nList, measureStartOffset=1.5)
>>> print(beamList)
[None,
 <music21.beam.Beams <music21.beam.Beam 1/start>>,
 <music21.beam.Beams <music21.beam.Beam 1/continue>>,
 <music21.beam.Beams <music21.beam.Beam 1/continue>>,
 <music21.beam.Beams <music21.beam.Beam 1/stop>>]

Fixed in v.7 – incomplete final measures in 6/8:

>>> sixEight = meter.TimeSignature('6/8')
>>> nList = [note.Note(type='quarter'), note.Note(type='eighth'), note.Note(type='eighth')]
>>> beamList = sixEight.getBeams(nList)
>>> print(beamList)
[None, None, None]

And Measure objects with paddingRight set:

>>> twoFour = meter.TimeSignature('2/4')
>>> m = stream.Measure([note.Note(type='eighth') for _ in range(3)])
>>> m.paddingRight = 0.5
>>> twoFour.getBeams(m)
[<music21.beam.Beams <music21.beam.Beam 1/start>>,
 <music21.beam.Beams <music21.beam.Beam 1/stop>>,
 None]
TimeSignature.getBeat(offset)

Given an offset (quarterLength position), get the beat, where beats count from 1

If you want a fractional number for the beat, see getBeatProportion.

TODO: In a future version – getBeat will probably do what getBeatProportion does now,

but just with 1 added to it.

>>> a = meter.TimeSignature('3/4', 3)
>>> a.getBeat(0)
1
>>> a.getBeat(2.5)
3
>>> a.beatSequence.partition(['3/8', '3/8'])
>>> a.getBeat(2.5)
2
TimeSignature.getBeatDepth(qLenPos, align='quantize')

Return the number of levels of beat partitioning given a QL into the TimeSignature. Note that by default beat partitioning always has a single, top-level partition.

The align parameter is passed to the offsetToDepth() method, and can be used to find depths based on start position overlaps.

>>> a = meter.TimeSignature('3/4', 3)
>>> a.getBeatDepth(0)
1
>>> a.getBeatDepth(1)
1
>>> a.getBeatDepth(2)
1

>>> b = meter.TimeSignature('3/4', 1)
>>> b.beatSequence[0] = b.beatSequence[0].subdivide(3)
>>> b.beatSequence[0][0] = b.beatSequence[0][0].subdivide(2)
>>> b.beatSequence[0][1] = b.beatSequence[0][1].subdivide(2)
>>> b.beatSequence[0][2] = b.beatSequence[0][2].subdivide(2)
>>> b.getBeatDepth(0)
3
>>> b.getBeatDepth(0.5)
1
>>> b.getBeatDepth(1)
2
TimeSignature.getBeatDuration(qLenPos)

Returns a Duration object representing the length of the beat found at qLenPos. For most standard meters, you can give qLenPos = 0 and get the length of any beat in the TimeSignature; but the simpler music21.meter.TimeSignature.beatDuration parameter, will do that for you just as well.

The advantage of this method is that it will work for asymmetrical meters, as the second example shows.

Ex. 1: beat duration for 3/4 is always 1.0 no matter where in the meter you query.

>>> ts1 = meter.TimeSignature('3/4')
>>> ts1.getBeatDuration(0.5)
<music21.duration.Duration 1.0>
>>> ts1.getBeatDuration(2.5)
<music21.duration.Duration 1.0>

Ex. 2: same for 6/8:

>>> ts2 = meter.TimeSignature('6/8')
>>> ts2.getBeatDuration(2.5)
<music21.duration.Duration 1.5>

Ex. 3: but for a compound meter of 3/8 + 2/8, where you ask for the beat duration will determine the length of the beat:

>>> ts3 = meter.TimeSignature('3/8+2/8')  # will partition as 2 beat
>>> ts3.getBeatDuration(0.5)
<music21.duration.Duration 1.5>
>>> ts3.getBeatDuration(1.5)
<music21.duration.Duration 1.0>
TimeSignature.getBeatOffsets()

Return offset positions in a list for the start of each beat, assuming this object is found at offset zero.

>>> a = meter.TimeSignature('3/4')
>>> a.getBeatOffsets()
[0.0, 1.0, 2.0]
>>> a = meter.TimeSignature('6/8')
>>> a.getBeatOffsets()
[0.0, 1.5]
TimeSignature.getBeatProgress(qLenPos)

Given a quarterLength position, get the beat, where beats count from 1, and return the amount of qLen into this beat the supplied qLenPos is.

>>> a = meter.TimeSignature('3/4', 3)
>>> a.getBeatProgress(0)
(1, 0)
>>> a.getBeatProgress(0.75)
(1, 0.75)
>>> a.getBeatProgress(1.0)
(2, 0.0)
>>> a.getBeatProgress(2.5)
(3, 0.5)

Works for specifically partitioned meters too:

>>> a.beatSequence.partition(['3/8', '3/8'])
>>> a.getBeatProgress(2.5)
(2, 1.0)
TimeSignature.getBeatProportion(qLenPos)

Given a quarter length position into the meter, return the numerical progress through the beat (where beats count from one) with a floating-point or fractional value between 0 and 1 appended to this value that gives the proportional progress into the beat.

For faster, integer values, use simply .getBeat()

>>> ts1 = meter.TimeSignature('3/4')
>>> ts1.getBeatProportion(0.0)
1.0
>>> ts1.getBeatProportion(0.5)
1.5
>>> ts1.getBeatProportion(1.0)
2.0

>>> ts3 = meter.TimeSignature('3/8+2/8')  # will partition as 2 beat
>>> ts3.getBeatProportion(0.75)
1.5
>>> ts3.getBeatProportion(2.0)
2.5
TimeSignature.getBeatProportionStr(qLenPos)

Return a string presentation of the beat.

>>> ts1 = meter.TimeSignature('3/4')
>>> ts1.getBeatProportionStr(0.0)
'1'
>>> ts1.getBeatProportionStr(0.5)
'1 1/2'
>>> ts1.getBeatProportionStr(1.0)
'2'
>>> ts3 = meter.TimeSignature('3/8+2/8')  # will partition as 2 beat
>>> ts3.getBeatProportionStr(0.75)
'1 1/2'
>>> ts3.getBeatProportionStr(2)
'2 1/2'

>>> ts4 = meter.TimeSignature('6/8')  # will partition as 2 beat
TimeSignature.getMeasureOffsetOrMeterModulusOffset(el)

Return the measure offset based on a Measure, if it exists, otherwise based on meter modulus of the TimeSignature.

>>> m = stream.Measure()
>>> ts1 = meter.TimeSignature('3/4')
>>> m.insert(0, ts1)
>>> n1 = note.Note()
>>> m.insert(2, n1)
>>> ts1.getMeasureOffsetOrMeterModulusOffset(n1)
2.0

Exceeding the range of the Measure gets a modulus

>>> n2 = note.Note()
>>> m.insert(4.0, n2)
>>> ts1.getMeasureOffsetOrMeterModulusOffset(n2)
1.0

Can be applied to Notes in a Stream with a TimeSignature.

>>> ts2 = meter.TimeSignature('5/4')
>>> s2 = stream.Stream()
>>> s2.insert(0, ts2)
>>> n3 = note.Note()
>>> s2.insert(3, n3)
>>> ts2.getMeasureOffsetOrMeterModulusOffset(n3)
3.0

>>> n4 = note.Note()
>>> s2.insert(5, n4)
>>> ts2.getMeasureOffsetOrMeterModulusOffset(n4)
0.0
TimeSignature.getOffsetFromBeat(beat)

Given a beat value, convert into an offset position.

>>> ts1 = meter.TimeSignature('3/4')
>>> ts1.getOffsetFromBeat(1)
0.0
>>> ts1.getOffsetFromBeat(2)
1.0
>>> ts1.getOffsetFromBeat(3)
2.0
>>> ts1.getOffsetFromBeat(3.5)
2.5
>>> ts1.getOffsetFromBeat(3.25)
2.25

Get the offset from beat 8/3 (2.6666): give a Fraction, get a Fraction.

>>> from fractions import Fraction
>>> ts1.getOffsetFromBeat(Fraction(8, 3))
Fraction(5, 3)

>>> ts1 = meter.TimeSignature('6/8')
>>> ts1.getOffsetFromBeat(1)
0.0
>>> ts1.getOffsetFromBeat(2)
1.5

Check that 2.5 is 2.5 + (0.5 * 1.5):

>>> ts1.getOffsetFromBeat(2.5)
2.25

Decimals only need to be pretty close to work. (But Fractions are better as demonstrated above)

>>> ts1.getOffsetFromBeat(2.33)
2.0
>>> ts1.getOffsetFromBeat(2.66)
2.5

Works for asymmetrical meters as well:

>>> ts3 = meter.TimeSignature('3/8+2/8')  # will partition as 2 beat
>>> ts3.getOffsetFromBeat(1)
0.0
>>> ts3.getOffsetFromBeat(2)
1.5
>>> ts3.getOffsetFromBeat(1.66)
1.0
>>> ts3.getOffsetFromBeat(2.5)
2.0

Let’s try this on a real piece, a 4/4 chorale with a one beat pickup. Here we get the normal offset for beat 4 from the active TimeSignature, but we subtract out the pickup length which is in a Measure’s paddingLeft property, and thus see the distance from the beginning of the measure to beat 4 in quarter notes

>>> c = corpus.parse('bwv1.6')
>>> for m in c.parts.first().getElementsByClass(stream.Measure):
...     ts = m.timeSignature or m.getContextByClass(meter.TimeSignature)
...     print(m.number, ts.getOffsetFromBeat(4.0) - m.paddingLeft)
0 0.0
1 3.0
2 3.0
...
TimeSignature.load(value: str, divisions=None)

Load up a TimeSignature with a string value.

>>> ts = meter.TimeSignature()
>>> ts.load('4/4')
>>> ts
<music21.meter.TimeSignature 4/4>

>>> ts.load('c')
>>> ts.symbol
'common'

>>> ts.load('2/4+3/8')
>>> ts
<music21.meter.TimeSignature 2/4+3/8>

>>> ts.load('fast 6/8')
>>> ts.beatCount
2
>>> ts.load('slow 6/8')
>>> ts.beatCount
6

Loading destroys all preexisting internal representations

TimeSignature.ratioEqual(other)

A basic form of comparison; does not determine if any internal structures are equal; o only outermost ratio.

TimeSignature.resetValues(value: str = '4/4', divisions=None)

reset all values according to a new value and optionally, the number of divisions.

TimeSignature.setAccentWeight(weights: Sequence[float] | float, level: int = 0) → None

Set accent weight, or floating point scalars, for the accent MeterSequence. Provide a list of float values; if this list is shorter than the length of the MeterSequence, it will be looped; if this list is longer, only the relevant values at the beginning will be used.

If the accent MeterSequence is subdivided, the level of depth to set is given by the optional level argument.

>>> a = meter.TimeSignature('4/4', 4)
>>> len(a.accentSequence)
4
>>> a.setAccentWeight([0.8, 0.2])
>>> a.getAccentWeight(0.0)
0.8...
>>> a.getAccentWeight(0.5)
0.8...
>>> a.getAccentWeight(1.0)
0.2...
>>> a.getAccentWeight(2.5)
0.8...
>>> a.getAccentWeight(3.5)
0.2...
TimeSignature.setDisplay(value, partitionRequest=None) → None

Set an independent display value for a meter.

>>> a = meter.TimeSignature()
>>> a.load('3/4')
>>> a.setDisplay('2/8+2/8+2/8')
>>> a.displaySequence
<music21.meter.core.MeterSequence {2/8+2/8+2/8}>
>>> a.beamSequence
<music21.meter.core.MeterSequence {{1/8+1/8}+{1/8+1/8}+{1/8+1/8}}>
>>> a.beatSequence  # a single top-level partition is default for beat
<music21.meter.core.MeterSequence {{1/8+1/8}+{1/8+1/8}+{1/8+1/8}}>
>>> a.setDisplay('3/4')
>>> a.displaySequence
<music21.meter.core.MeterSequence {3/4}>

Methods inherited from Music21Object:

Methods inherited from ProtoM21Object:

TimeSignature instance variables

TimeSignature.accentSequence

A MeterSequence governing accent partitioning.

TimeSignature.beamSequence

A MeterSequence governing automatic beaming.

TimeSignature.beatSequence

A MeterSequence governing beat partitioning.

TimeSignature.displaySequence

A MeterSequence governing the display of the TimeSignature.

TimeSignature.symbol

A string representation of how to display the TimeSignature. can be “common”, “cut”, “single-number” (i.e., no denominator), or “normal” or “”.

TimeSignature.symbolizeDenominator

If set to True (default is False) then the denominator will be displayed as a symbol rather than a number. Hindemith uses this in his scores. Finale and other MusicXML readers do not support this so do not expect proper output yet.

Instance variables inherited from Music21Object:

SenzaMisuraTimeSignature

class music21.meter.base.SenzaMisuraTimeSignature(text=None)

A SenzaMisuraTimeSignature represents the absence of a TimeSignature

It is NOT a TimeSignature subclass, only because it has none of the attributes of a TimeSignature.

>>> smts = meter.SenzaMisuraTimeSignature('0')
>>> smts.text
'0'
>>> smts
<music21.meter.SenzaMisuraTimeSignature 0>

SenzaMisuraTimeSignature bases

SenzaMisuraTimeSignature read-only properties

Read-only properties inherited from Music21Object:

Read-only properties inherited from ProtoM21Object:

SenzaMisuraTimeSignature read/write properties

Read/write properties inherited from Music21Object:

SenzaMisuraTimeSignature methods

Methods inherited from Music21Object:

Methods inherited from ProtoM21Object:

SenzaMisuraTimeSignature instance variables

Instance variables inherited from Music21Object:

TimeSignatureBase

class music21.meter.base.TimeSignatureBase(id: str | int | None = None, groups: Groups | None = None, sites: Sites | None = None, duration: Duration | None = None, activeSite: stream.Stream | None = None, style: Style | None = None, editorial: Editorial | None = None, offset: OffsetQL = 0.0, quarterLength: OffsetQLIn | None = None, **keywords)

A base class for TimeSignature and SenzaMisuraTimeSignature to inherit from.

TimeSignatureBase bases

TimeSignatureBase read-only properties

Read-only properties inherited from Music21Object:

Read-only properties inherited from ProtoM21Object:

TimeSignatureBase read/write properties

Read/write properties inherited from Music21Object:

TimeSignatureBase methods

Methods inherited from Music21Object:

Methods inherited from ProtoM21Object:

TimeSignatureBase instance variables

Instance variables inherited from Music21Object:

Functions

music21.meter.base.bestTimeSignature(meas: stream.Stream) → music21.meter.TimeSignature

Given a Measure (or any Stream) with elements in it, get a TimeSignature that contains all elements.

Note: this does not yet accommodate triplets.

>>> s = converter.parse('tinynotation: C4 D4 E8 F8').flatten().notes
>>> m = stream.Measure()
>>> for el in s:
...     m.insert(el.offset, el)
>>> ts = meter.bestTimeSignature(m)
>>> ts
<music21.meter.TimeSignature 3/4>

>>> s2 = converter.parse('tinynotation: C8. D16 E8 F8. G16 A8').flatten().notes
>>> m2 = stream.Measure()
>>> for el in s2:
...     m2.insert(el.offset, el)
>>> ts2 = meter.bestTimeSignature(m2)
>>> ts2
<music21.meter.TimeSignature 6/8>

>>> s3 = converter.parse('C2 D2 E2', format='tinyNotation').flatten().notes
>>> m3 = stream.Measure()
>>> for el in s3:
...     m3.insert(el.offset, el)
>>> ts3 = meter.bestTimeSignature(m3)
>>> ts3
<music21.meter.TimeSignature 3/2>

>>> s4 = converter.parse('C8. D16 E8 F8. G16 A8 C4. D4.', format='tinyNotation').flatten().notes
>>> m4 = stream.Measure()
>>> for el in s4:
...     m4.insert(el.offset, el)
>>> ts4 = meter.bestTimeSignature(m4)
>>> ts4
<music21.meter.TimeSignature 12/8>

>>> s5 = converter.parse('C4 D2 E4 F2', format='tinyNotation').flatten().notes
>>> m5 = stream.Measure()
>>> for el in s5:
...     m5.insert(el.offset, el)
>>> ts5 = meter.bestTimeSignature(m5)
>>> ts5
<music21.meter.TimeSignature 6/4>

>>> s6 = converter.parse('C4 D16.', format='tinyNotation').flatten().notes
>>> m6 = stream.Measure()
>>> for el in s6:
...     m6.insert(el.offset, el)
>>> ts6 = meter.bestTimeSignature(m6)
>>> ts6
<music21.meter.TimeSignature 11/32>

Complex durations (arose in han2.abc, number 445)

>>> m7 = stream.Measure()
>>> m7.append(note.Note('D', quarterLength=3.5))
>>> m7.append(note.Note('E', quarterLength=5.5))
>>> ts7 = meter.bestTimeSignature(m7)
>>> ts7
<music21.meter.TimeSignature 9/4>