@temper.sh/pitch

A TypeScript library for working with pitch, intervals, and pitch collections in arbitrary equal temperament systems.

Installation

npm install @temper.sh/pitch

Features

• Pitch Class Operations: Convert MIDI pitches to pitch classes
• Interval Calculations: Calculate intervals between pitches and interval classes
• Normal Order: Find the most compact representation of pitch collections
• Set Theory: Tools for analyzing pitch collections using music theory principles
• Equal Temperament Support: Works with any equal division of the octave (12-TET, 24-TET, etc.)

Core Types

type Pitch = number           // MIDI pitch (60 = middle C)
type PitchClass = number      // Pitch class (0-11 in 12-TET)
type Chord = Array<Pitch>     // Array of pitches
type Interval = number        // Semitone difference between pitches
type IntervalClass = number   // Smallest interval between given pitch classes

API Reference

Pitch Class

Convert MIDI pitches to pitch classes:

import { pitchClass } from '@temper.sh/pitch'

pitchClass(60)  // 0 (C)
pitchClass(61)  // 1 (C#)
pitchClass(72)  // 0 (C, octave higher)

Intervals

Calculate intervals between pitches:

import { interval, intervals } from '@temper.sh/pitch'

// Single interval
interval(60, 64)  // 4 (major third)

// All consecutive intervals in a chord
intervals([60, 64, 67])  // [4, 3] (major third, minor third)

Interval Classes

Calculate the smallest interval between pitch classes:

import { intervalClass } from '@temper.sh/pitch'

// From interval
intervalClass(7)   // 5 (perfect fourth, smaller than tritone)
intervalClass(11)  // 1 (minor second, smaller than major seventh)

// From two pitches
intervalClass(60, 67)  // 5

Normal Order

Find the most compact representation of a pitch collection:

import { normalOrder } from '@temper.sh/pitch'

normalOrder([60, 64, 67])      // [0, 4, 7] (C major triad)
normalOrder([67, 60, 64])      // [0, 4, 7] (same result, different input order)
normalOrder([61, 65, 68])      // [1, 5, 8] (C# major triad)

Music Theory Background

This library implements standard music theory concepts for computer-assisted analysis:

• Pitch Classes: Pitches reduced to their octave equivalents (C, C#, D, etc.)
• Normal Order: The most left-compressed arrangement of a pitch class set
• Interval Classes: The smallest possible interval between two pitch classes
• Equal Temperament: Musical tuning systems that divide the octave into equal parts

Development

# Install dependencies
pnpm install

# Run tests
pnpm test

# Run tests in watch mode
pnpm dev

# Build
pnpm build

# Format and lint
pnpm format-and-lint