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.
