This is a very simple demonstration of several built-in analytical functions in music21. We carry out a reduction of Bach chorale, analysis of harmony using Roman numerals and add Lerdahl and Jackendof type of metrical hierarchy.
The first code segment is to install music21 and other elements needed to run the environment. In Colab, press play and wait for all commands to be executed - this initial command might take some time as it needs to build the musi21 environment.
For instructions of how to get music21 and Musescore working on a local machine, see Installation guidelines from music21.
The script below uses a workaround where the excerpts are first written to a xml file and then converted to png image.
Harmonic and metrical analysis of an example excerpt bach/bwv30.6 using music21.
First get a Bach chorale.
from music21 import * # activate library
### 1 Select one example from Bach chorales
bwv30_6 = corpus.parse('bach/bwv30.6.xml')# Take an example
#bwv30_6.measures(1, 3).show() # Display 3 bars
bwv30_6.measures(1, 3).write('xml', fp='output.xml')
!mscore output.xml -o images/score1.png --trim-image 0zsh:1: command not found: mscore
Analyse chords using Roman numerals.
bChords = bwv30_6.chordify() # Slice the chords
for c in bChords.recurse().getElementsByClass('Chord'):
c.closedPosition(forceOctave=4, inPlace=True)
# Run analysis and add Roman numerals as lyrics
for c in bChords.recurse().getElementsByClass('Chord'):
rn = roman.romanNumeralFromChord(c, key.Key('A'))
c.addLyric(str(rn.figure))
bChords.measures(0, 3).show() # Display the result
bChords.measures(0, 3).write('xml', fp='output.xml')
!mscore output.xml -o images/score2.png --trim-image 0zsh:1: command not found: mscore
Carry out metrical analysis.
bass = bwv30_6.getElementById('Bass') # Get the bass part
excerpt = bass.measures(1,3) # Bar 1 through 3
analysis.metrical.labelBeatDepth(excerpt)# Metrical analysis
#excerpt.show() # Display the results
excerpt.write('xml', fp='output.xml')
!mscore output.xml -o images/score3.png --trim-image 0
!rm output.xmlzsh:1: command not found: mscore