PartWrite Harmony Lab icon
PartWrite Harmony Lab
Education · Four-voice workshop
Manuscript issue · Choir loft edition iOS · 2026

SATB bench · Rules before rehearsal

PartWrite Harmony Lab: the SATB bench that marks voice-leading before class does

Place four voices on a live grand staff, run a plain-language rules engine for parallels, spacing, doubling, and leading tones, then hear polyphonic playback and diff against seeded model chorales—built for AP Music Theory, choir leads, church pianists, and first-year conservatory work.

30+figured-bass lines in the ship deck
5 speciescounterpoint modes with dedicated checks
4-voiceSATB pad + solo/mute playback
On-deviceSwiftData drafts · no account required

Illustrative marketing figures; not App Store metrics.

About the workshop

PartWrite Harmony Lab is a four-voice workshop, not a chord dictionary and not another flashcard stack. You write on a color-stemmed SATB pad—pitch pickers, duration chips, accidentals, drag-to-retune, long-press rests—with range shading so each voice stays honest.

Hit the rules engine and it flags parallel fifths and octaves, voice crossing, wide spacing, illegal doubling, unresolved leading tones, and direct perfect intervals, each with a fix you can actually use. Lock a figured bass from the shipped deck, fill the upper parts, or work species 1–5 against a cantus firmus shelf with species-aware dissonance checks.

Homework becomes studio time before anyone else sees the page—drafts stay on-device, no account, no gallery of half-finished chorales on a server.

Label Roman numerals and cadences, spin the circle-of-fifths atlas, solo or mute voices in AVFoundation playback, loop a bar range, then export PDF/PNG. Built for AP Music Theory students, choir section leaders, church pianists, and conservatory freshmen who need the bench, not the dictionary.

Inside the manuscript

Six tools that keep the loft honest—from stem color to species bite.

I · PAD

Live SATB staff pad

Voice-color stems, range shading, pitch pickers, duration chips, and accidental toggles. Drag a note head to retune; long-press for a rest—zero empty placeholder measures.

II · ENGINE

Rules engine with plain fixes

Highlights parallel 5ths/8ves, crossing, spacing beyond an octave-plus-tone, illegal doubling, unresolved leading tones, and direct perfects—each hit opens a readable correction hint.

III · BASS

Figured bass + model diff

Thirty-plus multi-bar bass lines with figures locked in the content pack. Fill soprano–alto–tenor, reveal the model overlay, and see exactly where your voices diverge.

IV · SPECIES

Species 1–5 against cantus

Seeded cantus-firmus shelf with checks for note-against-note, dissonance prep/resolution, and climax placement before a drill can be marked complete.

V · SOUND

Voice-aware polyphonic playback

Mute or solo any part, scrub tempo, loop a selected bar range, and sound A440 before you sing or play along on the bench.

VI · ATLAS

Atlas, labels, export, daily bite

Circle-of-fifths wheel, tendency charts, doubling tables, Roman-numeral palette with answer keys, PDF/PNG export, on-device drafts, and a WidgetKit species bite that deep-links into the full lab.

Open the loft. Place the four voices. Let the engine mark the page—then listen before class does.

Contact PartWrite Harmony Lab