Choral Lab brings the art of four-part Bach chorale writing to your iPhone. Whether you're a composer, music student, or theory enthusiast, explore one of the most refined harmonic styles in Western music. Harmonize your melodies. Draw a soprano line on the interactive piano roll and watch Choral Lab instantly generate alto, tenor, and bass voices following authentic Bach voice-leading rules — avoiding parallel fifths and octaves, resolving leading tones, and building natural cadences. Browse 410 Bach chorales. Explore the complete corpus of J.S. Bach's four-part chorales with full score display, real-time chord analysis, and playback with rich choir sounds. Two ways to read the music. Switch between a traditional four-part score view with proper notation and clefs, or a piano roll view to see the voice leading clearly laid out across time. Mute individual voices to focus on any single part or study how voices interact. Generate original chorales. Let the app create complete chorales from scratch in any key — major or minor — with realistic harmonic progressions, passing tones, and Picardy thirds. Study chord analysis. Follow along with real-time Roman numeral chord labels as the music plays. Features: • Interactive soprano piano roll with tie support • Automatic SATB harmonization in Bach style • Library of 410 J.S. Bach chorales • Score view with Bravura music engraving font • Piano roll view with per-voice muting • Real-time chord analysis • Choir, piano, and organ sounds • MIDI export