Chord Thrower

A web tool for musicians practicing improvisation. It throws chords on screen to blow over in time with a built-in metronome, with difficulty tiers and common jazz patterns.

Features

• Chord drill — random chords flash on the beat. Four difficulty tiers that stack up: triads → 7th chords → extensions (9/11/13) → altered dominants. Lock to one key or draw from all 12. A difficulty-gated "next chord" preview helps on easy levels and hides on hard ones.
• Pattern practice — transposable jazz progressions (ii–V–I, turnarounds, blues, rhythm changes, tritone subs, backdoor ii–V, modal interchange, Bird blues, Giant Steps, …), grouped by difficulty. Loop in one key, cycle keys by fourths or at random each rep, and ramp the tempo every repetition.
• Metronome — accurate scheduling on Tone.Transport, adjustable tempo, time signatures (4/4, 3/4, 2/4, 6/8), accented downbeat, visual beat indicator, optional count-in.
• Voiced chord audio (optional) — hear each chord, not just see it.
• Instrument transposition — read chords in concert pitch or for B♭ / E♭ / F instruments.
• Settings persist in your browser; no account needed.

Tech

• Next.js (App Router) + TypeScript + Tailwind CSS
• Tonal.js — chord/scale theory and transposition
• Tone.js — audio clock, metronome, and chord synth

Development

npm install
npm run dev        # http://localhost:3000
npm test           # vitest — theory engine unit tests
npm run lint
npm run typecheck
npm run build

The music-theory engine lives in lib/theory/ (pure functions, unit-tested). Audio is in lib/audio/, the drill/pattern schedulers in lib/drill/ and lib/pattern/, and UI in components/.

Deploy

Zero-config on Vercel: import the GitHub repo and deploy. The app is fully client-side (static), so there is no server runtime cost.