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A simple python library to ingest and manipulate musical chords stored in plaintext format according to Christopher Harte's 2010 thesis.


python -m pip install ChordalPy

The format

The chords that this library can parse are in a specific plaintext format detailed here; however, here's a quick and dirty run down.

Each chord has three parts: the root, the intervals, and the bass. They are seperated with a colon and a slash like so



The root is simply any letter name. It could be 'C' or 'G#' or 'Fbbbbb'.


The intervals section consists of a shorthand abbreviation for a common set of intervals followed by any changes to those intervals in parantheses. For example, a major triad with an added sharp sixth would be maj(#6). The added intervals can do one of:

  1. Add an interval to the existing shorthand.
  2. Modify (sharp or flat) an interval in the existing shorthand.
  3. Remove an interval in the existing shorthand (notated with a * before the interval to be removed).

The list of shorthands can be found on page 105 of the earlier referenced PDF.


The bass is an interval degree (any digit 1-9) along with 0 or more modifiers (# or b)

A note on intervals

There is an interesting quirk to musical intervals that means they cannot be entirely expressed with only one digit. Rather, they requrie a tuple of two integers.

When looking through the source of this library, you will often find intervals notated as such. The first integer represents the number of letter names between the notes (for instance, in the interval from C to G the first integer would be 5) and the second integer is the number of half steps (so in the interval from C to G the second integer would be 7).

Using this method you can see how you would distiniguish between two enharmonic pitches. For example, C to E and C to Fb. The interval from C to E would be (3, 4) while the interval from C to Fb would be (4, 4).

Library Usage

Parse a chord and print its members

import ChordalPy

my_chord = ChordalPy.parse_chord("C:maj")
spelling = my_chord.get_spelling()
print("C:maj has notes %s" % spelling)

Instantiate a chord directly

import ChordalPy

# C major in first inversion (C:maj/3)
root = "C"
intervals = [(1, 0), (3, 4), (5, 7)]
bass = "E"

my_chord = ChordalPy.Chord(root, intervals, bass)

Chord Class

Print a string representation of a chord

# C:[(1, 0), (3, 4), (5, 7)]/E

Print the spelling of a chord

# ['C', 'E', 'G']

Print a binary note array of a chord

# [1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0]

Print a pseudohash of a chord's intervals

# ecca

Find the note a given interval above a chord's root

print(my_chord.note_from_interval([5, 8]))
# ecca

See Also

Projects - A web tool that uses machine learning to generate chord progressions. The machine learning model was trained on data created with this library.


A non-exhaustive list of datasets that use a format parsable by this library:


A simple python library to ingest and manipulate musical chords stored in plaintext format