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Music21

These are RBD\'s notes on Music21. Probably this does not belong in AMADS but it\'s a reference to help understand Music21.

https://www.music21.org/music21docs/usersGuide/

Note class

  • name: e.g. 'F'
  • octave: e.g. 5 (ISO)
  • pitch: e.g. 'F5', 'B-2', 'D#3'

Maybe it would make more sense to have an alter (alteration)? Music21 uses, e.g. bflat.pitch.accidental.alter == -1, so alterations are actually objects, maybe because they have some interesting attributes like position \'left\' or \'above\'

Canonical note representation could be: * <start, duration, pitch, lyric> (see Pitch and Duration below)

derived from this are: * name_with_octave * pitch_class * frequency * alter_name * key_number (or maybe midi) * unicode_name * unicode_name_with_octave

methods include: * enharmonic() * lower_enharmonic() * upper_enharmonic()

Rests class - another class. Accessing pitch gives an exception

For convenience, Note has a lot of methods, but Note should be composed of: * <start, duration, pitch, tie>, where tie is 'start', 'stop', or 'continue' (both)

Pitch is <name, octave, alter> and derived are: * name_with_octave * pitch_class * frequency * alter_name * key_number (or maybe midi) * unicode_name * unicode_name_with_octave

methods include: * enharmonic() * lower_enharmonic() * upper_enharmonic()

Duration using rationals - see fractions.py

measured in quarters

properties are:

  • quarters

Structure

Stream is supertype for Score, Part and Measure Streams have time (delta) and a list of components: * Stream * Note * Chord * Clef * TimeSignature * Rest?

Component deltas are relative to the parent, not global.

We can add a tempo curve that consists of breakpoints starting at (0,0), and map seconds to quarters Operations could then include: fix the tempo, e.g.

linear mapping at some number of quarters/second; convert internal deltas from quarters to seconds; convert internal deltas from seconds to quarters.

Ties: in Music21, notes can have durations that take them out of the measure, OR notes can have ties.

Chord

similar to Note, but it has pitches instead of pitch methods include: * root * bass

Tempo

not in Music21 - should add tempo curve to Stream