User’s Guide, Chapter 3: Pitches, Durations, and Notes again

Now that you’ve made a couple of Note objects, it’s time to dig a little deeper into what makes a Note really a Note, namely, music21.pitch, and music21.duration objects.

The Pitch object

Since we’ve already covered Note objects, Pitch objects will be a breeze. Just like how the Note object is found in the note module, the Pitch object is found in the pitch module.

Let’s create a Pitch. Like we did with Notes, just class the class with a note name, such as B with the optional symbols for sharp or flat, (# or - respectively).

You can put an octave number after the name (4 = low treble clef), but you don’t have to:

from music21 import *
p1 = pitch.Pitch('b-4')

Here we’ll use a more abstract variable name, p1 for our first Pitch, just in case we change the pitch later (via .transpose() or something else).

Just like we saw with Notes there are a lot of attributes (a.k.a. properties; we’ll use the term interchangeably for a bit before we talk about the difference) and methods that describe and change pitches. The first three will be old hat from Note objects:

p1.octave

 4

p1.pitchClass

 10

p1.name

 'B-'

p1.accidental.alter

 -1.0

Here are two more that you can use. The first is pretty self-explanatory. The second gives the value of the Pitch in the older, “MIDI” representation that is still in use today. It’s a number between 0 and 127 where middle C (C4) is 60 and C#4/Db4 is 61, B3 is 59, etc.

p1.nameWithOctave

 'B-4'

p1.midi

 70

Most of these attributes can be changed (they are “settable properties” in Python speak).

When an attribute is set, the Pitch object changes whatever is necessary to reflect the new value:

p1.name = 'd#'
p1.octave = 3
p1.nameWithOctave

 'D#3'

And our familiar .transpose() method also appears on Pitch as well. Remember that p1 is now a D#:

p2 = p1.transpose('M7')
p2

 <music21.pitch.Pitch C##4>

Notice that at the command line, just printing the variable name gives you the representation <music21.pitch.Pitch C##4>. You can also get this by typing repr(p2).

So, there’s really nothing new about Pitch objects that you didn’t already know from learning about Notes. So why the two different objects? It turns out, they are so similar because actually every Note object has a Pitch object inside it (like the monster in Alien but more benign). Everything that we did with the note.Note object, we could do with the note.Note.pitch object instead:

csharp = note.Note('C#4')
csharp.name

 'C#'

csharp.pitch.name

 'C#'

csharp.octave

 4

csharp.pitch.octave

 4

But pitch objects have a lot more to offer for more technical working, for instance, Pitch objects know their names in Spanish:

csharp.pitch.spanish

 'do sostenido'

Notes don’t:

csharp.spanish

---------------------------------------------------------------------------

AttributeError                            Traceback (most recent call last)

<ipython-input-16-a0f0e2502262> in <module>
----> 1 csharp.spanish


AttributeError: 'Note' object has no attribute 'spanish'

Here are some other things you can do with Pitch objects. Get the sharp printed nicely:

print(csharp.pitch.unicodeName)

 C♯

Get some enharmonics – these are methods, so we add () to them:

print( csharp.pitch.getEnharmonic() )
print( csharp.pitch.getLowerEnharmonic() )

 D-4
 B##3

By the way, you know how we said that you shouldn’t have a variable named pitch because there’s already a module named pitch. You might wonder why Note objects can have an attribute named pitch without causing any problems. It’s because the .pitch attribute is always attached to a Note , so it’s never used without a prefix of some sort (in this case, csharp.pitch ), and that’s enough to prevent any trouble.

So far, it looks like Pitch objects can do everything Note objects can do and more. So why do we need Note objects? It’s because they also have Duration attributes, as we’ll see in the next section. Without a Duration attribute, you cannot put an object into a Measure or show it on your screen.

Carving time with Duration objects

For a Note to occupy musical space, it has to last a certain amount of time. We call that time the Note’s Duration. Duration objects are ubiquitous in music21. Nearly all objects have, or can have, a Duration. A Duration object can represent just about any time span.

Duration objects are best used when they’re attached to something else, like a Note or a Rest, but for now, let’s look at what we can do with them on their own.

Duration objects reside in the duration module. When you create a Duration object, you can say what type of duration you want it to be when you create it.

Here we’ll create the duration of a half note:

halfDuration = duration.Duration('half')

The string “half” is called the “type” of the Duration. Music21 Durations use the common American duration types: “whole”, “half”, “quarter”, “eighth”, “16th”, “32nd”, “64th”. Note that for durations shorter than an eighth note, we use numbers instead of spelling out the whole name of the Duration type. Music21 also supports less commonly used types such as “breve” (2 whole notes), “longa” (4 whole notes), and “maxima” (8 whole notes) and on the other side, “128th”, “256th”, etc. down to “2048th” notes. (Some of these very long and very short notes can’t be displayed in many musical notation systems, but it’s good to know that we’re ready when they are).

The other standard way of creating a Duration is by passing it a number when it is created. That number represents how many quarter notes long it is. So we could have created our half note Duration by saying 2 or 2.0. But we can also create Durations that aren’t exactly “whole”, “half”, “quarter”, etc. Let’s create a dotted quarter note, which is 1.5 quarter notes long:

dottedQuarter = duration.Duration(1.5)

As with the Pitch and Note objects we’ve already seen, there are a bunch of attributes that Duration objects have. The most important one is .quarterLength. The quarterLength of our dottedQuarter variable is of course 1.5: we set it to be. But just as importantly, the halfDuration object also has its quarterLength set:

dottedQuarter.quarterLength

 1.5

halfDuration.quarterLength

 2.0

The .type attribute tells you what general type of Duration you have:

halfDuration.type

 'half'

dottedQuarter.type

 'quarter'

The type attribute cannot be everything that describes the Duration, there has to be some place where music21 keeps track of the fact that the dottedQuarter variable has a dot (otherwise it wouldn’t have a quarterLength of 1.5). You’ll find the attribute called .dots:

halfDuration.dots

 0

dottedQuarter.dots

 1

The attributes of dots, type, and quarterLength are actually special attributes called “properties”. A property is an attribute that is smart in some way. Let’s change the number of dots on our dottedQuarter object and see what happens to the quarterLength property:

dottedQuarter.dots = 2
dottedQuarter.quarterLength

 1.75

dottedQuarter.dots = 3
dottedQuarter.quarterLength

 1.875

dottedQuarter.dots = 4
dottedQuarter.quarterLength

 1.9375

Or let’s change the quarterLength of the dottedQuarter and see what happens to the type and dots:

dottedQuarter.quarterLength = 0.25
dottedQuarter.type

 '16th'

dottedQuarter.dots

 0

QuarterLengths are so important to music21 that we’ll sometimes abbreviate them as qL or qLs. Almost everything that is measured in music21 is measured in qLs.

Music21 can also deal with other quarterLengths such as 0.8, which is 4/5ths of a quarter note, or 1/3, which is an eighth note triplet. (For this reason, users compiling spreadsheets or other text-based output should expect to find the occasional quarterLength expressed as a Fraction.)

(You can go ahead and make a triplet or other Tuplet, but we’ll get to triplets, including tips for manipulating a Fraction in Chapter 19).

Back to Notes

So now you can see the advantage of working with Note objects: they have both a .pitch attribute, which contains a Pitch object, and a .duration attribute, which contains a Duration object. The default Pitch for a Note is C (meaning C4) and the default Duration is 1.0, or a quarter note.

n1 = note.Note()
n1.pitch

 <music21.pitch.Pitch C4>

n1.duration

 <music21.duration.Duration 1.0>

But we can play around with them:

n1.pitch.nameWithOctave = 'E-5'
n1.duration.quarterLength = 3.0

and then the other properties change accordingly:

n1.duration.type

 'half'

n1.duration.dots

 1

n1.pitch.name

 'E-'

n1.pitch.accidental

 <music21.pitch.Accidental flat>

n1.octave

 5

We already said that some of the attributes of Pitch can also be called on the Note object itself. The same is true for the most important attributes of Duration:

n1.name

 'E-'

n1.quarterLength

 3.0

Let’s change the quarterLength back to 1.0 for now:

n1.quarterLength = 1.0

Notes can do things that neither Pitch or Duration objects can do. For instance, they can have lyrics. Let’s add some lyrics to Notes. You can easily set Lyric objects just by setting the lyric property. (For reference, the lyric attribute is actually an attribute of GeneralNote, which is a “base class” from which the Note class “inherits”. In other words, the Note class gains the lyric attribute from GeneralNote. But that’s not too important.)

otherNote = note.Note("F6")
otherNote.lyric = "I'm the Queen of the Night!"

But let’s do something more complex. Here I add multiple lyrics to n1 using the Note's addLyric() method. And instead of adding a simple String, I’ll add as a lyric the name of the note itself and its pitchClassString.

n1.addLyric(n1.nameWithOctave)
n1.addLyric(n1.pitch.pitchClassString)

Finally, lets put the quarterLength of the note as a string with a preface “QL:”:

n1.addLyric(f'QL: {n1.quarterLength}')

The placement of an “f” before the string f'QL: {n1.quarterLength}’ says to substitute anything in {} with its actual value as a string. (Remember that .quarterLength is not a string, but a float).

As it should be becoming clear, we can always check our work with the show() method.

n1.show()

If we now edit the quarterLength property we can still change the Note’s Duration. But because we already set the lyric to show “QL: 1.0, it won’t be changed when we .show() it again in the following example.

n1.quarterLength = 6.25
n1.show()

There are many more things we can do with a Note object, but I’m itching to look at what happens when we put multiple Notes together in a row. And to do that we’ll need to learn a bit about the topic of Chapter 4: Streams.