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pytheory/docs/index.rst
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kennethreitz b396f42f84 Add REPL guide: theory scratchpad, composition, effects, complete example
Covers the prompt, theory commands, composition flow, effects,
automation, LFOs, playback, export, and a full start-to-finish session.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-25 21:26:11 -04:00

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PyTheory: Music Theory for Humans
=================================
**PyTheory** is a Python library for exploring music theory, composing
multi-part arrangements, and exporting them to MIDI for your DAW.
Use it to learn theory by doing — build chords from intervals and hear
the result. Use it to sketch song ideas faster than clicking through a
DAW. Use it with Claude Code to prototype
music from natural language. Or just use it to answer "what chords are
in G major?" without opening a browser.
::
$ pip install pytheory
Theory
------
The theory layer works everywhere Python runs — no audio setup needed.
Tones, scales, chords, keys, intervals, harmony, 6 musical systems,
25 instruments:
.. code-block:: pycon
>>> from pytheory import Key, Chord, Tone
>>> Key("C", "major").chords
['C major', 'D minor', 'E minor', 'F major', 'G major', 'A minor', 'B diminished']
>>> [c.symbol for c in Key("G", "major").progression("I", "V", "vi", "IV")]
['G', 'D', 'Em', 'C']
>>> Chord.from_symbol("F#m7b5").identify()
'F# half-diminished 7th'
>>> Tone.from_string("C4").interval_to(Tone.from_string("G4"))
'perfect 5th'
Composition
-----------
When you're ready to make noise, the composition layer adds drums,
synths, effects, and multi-part arrangements. Sketch an idea, hear
it through your speakers, export MIDI, finish in your DAW:
.. code-block:: python
from pytheory import Score, Pattern, Key, Duration, Chord
from pytheory.play import play_score
score = Score("4/4", bpm=140)
score.drums("bossa nova", repeats=4)
chords = score.part("chords", synth="fm", envelope="pad", reverb=0.4)
lead = score.part("lead", synth="saw", envelope="pluck", delay=0.3)
bass = score.part("bass", synth="sine", lowpass=500)
for chord in Key("A", "minor").progression("i", "iv", "V", "i"):
chords.add(chord, Duration.WHOLE)
lead.arpeggio("Am", bars=4, pattern="updown", octaves=2)
play_score(score)
score.save_midi("sketch.mid")
Or hear a randomly generated track from the command line — different
every time::
$ pytheory demo
What's Inside
-------------
- **Theory** — tones, scales (40+ across 6 systems), chords (17 types),
keys, Roman numeral analysis, modulation, voice leading
- **Sequencing** — Score, Parts, arpeggiator, legato/glide, velocity,
swing, humanize, tempo changes, song sections
- **Synthesis** — 10 waveforms, 8 envelopes, 58 drum patterns, 21 fills
- **Effects** — reverb (algorithmic + 7 convolution IRs), delay, lowpass,
distortion, chorus, sidechain, automation, LFOs
- **Instruments** — 25 presets with fingering generation
- **Export** — MIDI, WAV, real-time playback
- **CLI**``pytheory demo``, ``key``, ``chord``, ``midi``, ``play``, and more
- **AI-friendly** — Claude Code can compose
and play music through PyTheory from natural language
.. toctree::
:maxdepth: 2
:caption: User Guide
guide/quickstart
guide/theory
guide/tones
guide/scales
guide/chords
guide/fretboard
guide/systems
guide/sequencing
guide/synths
guide/effects
guide/drums
guide/playback
guide/repl
guide/cli
guide/cookbook
.. toctree::
:maxdepth: 2
:caption: API Reference
api/tones
api/scales
api/chords
api/charts
api/play
api/systems
.. toctree::
:maxdepth: 1
:caption: Project
changelog