Play one note. Hear four centuries answer.
Chorale Generator puts the harmony of Bach, the hymnal and the Renaissance under your melody, one note at a time. It shows you the chord the masters reached for, where they went next, and writes it out in four parts.
Runs in your browser. No sign-up, no download. Works with a MIDI keyboard.
What it is
Every chorale is a lineage. A melody is handed down, and each generation sets it with the chords of its time.
Chorale Generator lets you sit inside that lineage. Choose a key, play a melody note, and it shows the chord most often placed beneath that note, ranked by how often it was actually chosen. Play the next note and it weighs what came before, the way a composer would. Underneath, it lays out soprano, alto, tenor and bass by the classical rules of voice leading, so what you hear is a real four-part setting, not a stack of chords.
It is a practice partner for your ear and your hands, a sketchpad for producers, and a working library of how harmony has been done.
Three schools of harmony
Switch styles and the same melody is reharmonized by a different tradition. Each style is built from real music, not guesswork.
Bach
The source of four-part writing as we teach it. Every beat of 351 of J.S. Bach's four-part chorales was analyzed, so each suggestion is what Bach actually did after that chord, with that melody note. Secondary dominants, cadential 6/4s, the pull of the leading tone: all of it, in his proportions.
Hymnal
The sound of the church piano and the Sunday service. Chord progressions were read from 91 hymns across a hymn fake book, chord by chord, and turned into a map of where hymn harmony moves. Plainer, warmer, and built on I, IV and V, with the plagal turns gospel players will recognize.
Renaissance
Before major and minor, there were modes. This style reads the four-voice tables of Athanasius Kircher's Arca musarithmica (1650), a composing machine in a wooden box, in Dorian, Phrygian, Mixolydian, Ionian and Aeolian. Musica ficta, period voice ranges and the open “low fifth” give it the sound of a Renaissance choir.
Features
- Harmonize as you play. Each melody note gets its most likely chords, ranked with percentages. Click any one to swap it in.
- See where the music goes next. After every chord, the app shows that tradition's most common next moves, and lights up the melody notes that usually follow.
- Compose a melody. One click writes a new chorale tune in your key, 2 to 6 phrases long, following the rules of good melody: mostly stepwise, leaps that turn back, one high point, real cadences. Then it harmonizes it.
- Import MIDI. Drop in any MIDI file. The app finds the melody or soprano line, detects the key, marks the phrase endings and harmonizes it in the style you choose.
- True four-part voice leading. Soprano, alto, tenor and bass are laid out across the whole piece: no parallel fifths or octaves, leading tones rise, sevenths fall, voices stay in range. Every chord gets a rules check.
- Read it like a musician. Grand staff notation, Roman numerals, lead-sheet chord symbols, extended “color” symbols, or figured bass, the way Bach himself thought.
- Watch the voices. A keyboard under the score shows every chord's four voices, color-coded by root, third, fifth and seventh.
- Embellish. Add passing notes and cadential 4–3 suspensions to the playback for a more Baroque line.
- Take it to your DAW. Export a four-track MIDI file, one track per voice.
How it works
Choose a key and a style.
Pick a tonic, major, minor or a church mode, and a tradition: Bach, Hymnal or Renaissance.
Give it a melody.
Play notes on the on-screen keyboard, your computer keys or a MIDI keyboard. Or compose a tune, or import a MIDI file.
Hear the answer.
Each note gets its chord and a full four-part voicing. Swap chords, mark phrase endings, play it back, and export it as MIDI.
Who it's for
- Producers and beatmakers. Turn a hook into a choir-ready progression, then drag the four voices into your DAW as separate tracks.
- Keyboardists and guitarists. Learn the chords that sit under a melody by hearing them, not memorizing them.
- Theory students. See Roman numerals, figured bass and voice-leading rules applied to real music, with the reason behind every choice.
- Church and gospel musicians. Reharmonize a hymn tune in Bach's style, the hymnal's, or a Renaissance mode.
- Teachers. Project it in class: play a melody and let the room hear how three traditions answer it.
Sources and credits
Chorale Generator stands on the work of the masters and the scholars who preserved them.
- J.S. Bach — 351 four-part chorales (the Riemenschneider collection, via the open-source music21 corpus), analyzed beat by beat.
- C.P.E. Bach — his chord catalogue from the Essay on the True Art of Playing Keyboard Instruments, as summarized by Christopher Czarnecki in J.S. Bach: 413 Chorales Analyzed, guides the figured-bass display and the dissonance rules.
- The hymnal tradition — chord progressions from a sample of 91 hymns in The Hymn Fake Book (Hal Leonard). Only chord-to-chord counts are used; no notation is reproduced.
- Athanasius Kircher — Arca musarithmica (1650), Syntagma I, from Andrew A. Cashner's digital edition at arca1650.info.
- Renaissance performance practice — musica ficta and voice ranges after Alexander Blachly in Jeffery Kite-Powell, ed., A Performer's Guide to Renaissance Music; sonority and spacing after “Orchestration of Sonorities in Renaissance Polyphony” (timbreandorchestration.org).
Designed and built by Edward “Ed The Wave” Thompson-Matthews.
FAQ
The melody is yours. The lineage is waiting.
Open Chorale Generator, play a note, and hear how Bach, the hymnal and the Renaissance would answer it.