Jazzify

This is a JavaScript port of lucainiaoge's Jazzify, an open-source rule-based jazzification system.

Jazzify is rule-based. Apart from its capability to serve as an engine of computational jazz music theory, Jazzify is able to accomplish tasks including chord-symbol identification, key detection, chord extension, and chord-to-voicing.

Features

Chord Symbol Identification

Jazzify is able to convert list of pitches into its corresponding jazz chord symbol, in format (root_note, chord_type, bass_note).

Key Detection

Jazzify is able to give the (function, key) guesses for each chord, given a chord progression. For example, given chord progression [C, D, F, G, G-, C7, F], Jazzify is able to output [(T,C), (DD,C), (S,C), (D,C), (S,F), (D,F), (T,F)].

Jazzify takes account of tonic (T), dominant (D), subdominant (S), double-dominant (DD), and Napoleon (N) functions. Other functions like the leading seventh can be converted into the existing categories.

Chord Extension

Jazzify is able to suggest contextually appropriate chord extensions based on harmonic function and key context.

Installation

npm install jazzify

Quick Start

import { identifyChord, detectKey, PitchNames } from 'jazzify';

// Identify a chord from MIDI notes
const chordName = identifyChord([60, 64, 67, 70]);
console.log(chordName); // ["C-dominant-seventh"]

// Identify using pitch names
const notes = PitchNames.listPitchNameToNum(['C4', 'E4', 'G4', 'Bb4']);
console.log(identifyChord(notes)); // ["C-dominant-seventh"]

// Analyze a chord progression (ii-V-I in C major)
const progression = [
  [62, 65, 69],      // Dm
  [67, 71, 74, 77],  // G7
  [60, 64, 67]       // C
];
const analysis = detectKey(progression);
console.log(analysis.keys);      // ["C-Major", "C-Major", "C-Major"]
console.log(analysis.functions); // ["subdominant", "dominant", "tonic"]

API Reference

Chord Identification

identifyChord(notes)

Identify a chord from an array of MIDI note numbers.

import { identifyChord } from 'jazzify';

identifyChord([60, 64, 67]);           // ["C-Major"]
identifyChord([60, 63, 67]);           // ["C-Minor"]
identifyChord([60, 64, 67, 71]);       // ["C-Major-seventh"]
identifyChord([60, 64, 67, 70]);       // ["C-dominant-seventh"]
identifyChord([60, 63, 66]);           // ["C-diminished"]
identifyChord([60, 64, 68]);           // ["C-augmented"]

notesToChordSymbol(notes, detectInversion, listAll, returnMidiNum)

Get detailed chord analysis with root, quality, and bass.

import { notesToChordSymbol } from 'jazzify';

// Basic usage
const result = notesToChordSymbol([60, 64, 67]);
// [{ root: 60, quality: "Major", bass: null }]

// Detect inversions (E in bass = C/E)
const inverted = notesToChordSymbol([64, 67, 72], true);
// Returns both root position and inversion interpretations

Key Detection

detectKey(chordProgression)

Analyze a chord progression to determine keys and harmonic functions.

import { detectKey } from 'jazzify';

// Analyze a ii-V-I-IV progression
const chords = [
  [62, 65, 69],     // Dm
  [67, 71, 74],     // G
  [60, 64, 67],     // C
  [65, 69, 72]      // F
];

const analysis = detectKey(chords);
console.log(analysis.functions); // ["subdominant", "dominant", "tonic", "subdominant"]
console.log(analysis.keys);      // ["C-Major", "C-Major", "C-Major", "C-Major"]

Chord Extensions

getExtensions(chordType, chordRoot, key)

Get contextually appropriate chord extensions based on harmonic context.

import { getExtensions, ChordSymbols } from 'jazzify';

// Get extensions for a ii chord (Dm) in C major
getExtensions(ChordSymbols.MINOR, 2, 0);  // ["Minor-ninth"]

// Get extensions for a V chord (G) in C major
getExtensions(ChordSymbols.MAJOR, 7, 0);  // ["dominant-13th", "dominant-seventh"]

Pitch Utilities

import { PitchNames } from 'jazzify';

// Convert pitch names to MIDI numbers
PitchNames.listPitchNameToNum(['C4', 'E4', 'G4']); // [60, 64, 67]

// Convert MIDI to pitch name
PitchNames.midiToPitchName(60); // "C4"

// Pitch name to MIDI
PitchNames.pitchNameToMidi('C4'); // 60

CLI

Jazzify includes an interactive CLI for chord analysis:

npx jazzify

🎹 Welcome to Jazzify CLI - Jazz Theory Analysis Tool

jazzify > C4 E4 G4
  Notes: C4 E4 G4 (MIDI: 60, 64, 67)
  Chord: C-Major

jazzify > C4 E4 G4 Bb4
  Notes: C4 E4 G4 Bb4 (MIDI: 60, 64, 67, 70)
  Chord: C-dominant-seventh

jazzify > key
  ═══ Key Analysis ═══
  1. C-Major              │ subdominant  │ C-Major
  2. C-dominant-seventh   │ dominant     │ C-Major

Module Exports

Core Modules

• Intervals - Musical interval constants and utilities
• PitchNames - Pitch name/MIDI conversion utilities
• Scales - Scale definitions
• ChordSymbols - Chord quality constants

Main Functions

• identifyChord - Simple chord identification
• notesToChordSymbol - Detailed chord analysis
• detectKey - Key and harmonic function analysis
• getExtensions - Context-aware chord extensions

Supported Chord Types

Jazzify recognizes a comprehensive set of jazz chord qualities:

| Category | Chord Types | |----------|-------------| | Major | Major, Major 7th, Major 9th, Major 6th, Major 6/9, Major #11 | | Minor | Minor, Minor 7th, Minor 9th, Minor 6th, Minor 6/9, Minor-Major 7th | | Dominant | Dominant 7th, Dominant 9th, Dominant 11th, Dominant 13th, Altered | | Suspended | Sus4, Sus2, Sus 7th, Sus 13th | | Diminished | Diminished, Diminished 7th, Half-diminished 7th | | Augmented | Augmented, Augmented Major 7th |

ESM and CommonJS

Jazzify supports both ES modules and CommonJS:

// ES Modules
import { identifyChord } from 'jazzify';

// CommonJS
const { identifyChord } = require('jazzify');

TypeScript

TypeScript declarations are included for full type support.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Credits

This is a JavaScript port of the original Jazzify Python library created by lucainiaoge. The original system includes additional capabilities such as melody swingification, walking bass generation, and bossa nova style transformation.

JavaScript port by Elijah Melton.

License

MIT