voiceCipher

Harmonic voice-leading cipher notation for music21 scores

This Python package takes a multi-voice score and annotates each part with lyrics showing the harmonic interval and motion type between adjacent parts. Useful for counterpoint analysis, teaching, and checking student work.

Built on music21 — a toolkit for computer-aided musical analysis.

Example

Bach BWV 66.6:

Cipher symbols

Symbol	Motion
(none)	Oblique motion
=	Parallel motion
<	Contrary motion (outward)
>	Contrary motion (inward)
↗	Direct motion (ascending)
↘	Direct motion (descending)

In the example above the notation on the Soprano refers to the relation between Soprano and Alto; at the Alto part, the cipher corresponds to the relation Alto-Tenor and so on. The Bass part cipher reflects Soprano-Bass relation.

Installation

pip install git+https://github.com/matiasnm/voiceCipher.git

Or for development:

git clone https://github.com/matiasnm/voiceCipher.git
cd voiceCipher
pip install -e .

Usage

As a Python library

from voiceCipher import voiceCipher
from music21 import corpus

score = corpus.parse("bwv66.6")
result = voiceCipher(score, measureBreak=4)
result.show()

From the command line

# Run demo with Bach BWV 66.6
python -m voiceCipher

# Cipher your own MusicXML file
python -m voiceCipher my_score.xml

After pip install -e ., you also get a voicecipher command:

voicecipher my_score.xml

Render to PNG

If you have MuseScore 4 installed:

python render_to_png.py
python render_to_png.py my_score.xml

Requirements

• Python ≥ 3.10
• music21 ≥ 10.5.0
• (optional) MuseScore 4 for PNG rendering