Triad trainer for a USB MIDI keyboard. Names a chord, you play it, it times you.
A personal drill for major and minor triads on a MIDI keyboard. The app names a chord, you play it,
it validates and times you. Reaction time is the metric worth watching, not the score: the goal is
not working the chord out, it is knowing it immediately.
Learn covers the same 24 chords three ways: the four hand shapes they sort into, the three
inversions, and the scale each one comes from.
Drill names a chord and times how long you take to play it. Turn on Ask for inversions and the
prompt names a voicing too, so C major / 1st inversion wants E at the bottom.
Ear plays a chord instead of naming one. Find it on the keyboard. R plays it again, and
listening twice costs you the time it costs you. A miss retries the same chord, so the name stays
hidden unless you turn on Name the answer.
Explore is free play. It names whatever you hold, with the inversion and the fingering for both
hands.
A mastery grid shows all 24 chords by accuracy, so the weak ones are visible rather than remembered.
Underneath the timing readouts, a day streak counts consecutive days with at least one correct
answer, next to a daily target of 20. Everything is derived from the last 500 attempts, which makes
it recent form rather than a lifetime record.
The keys play a real piano: fourteen samples from Alexander Holm’s Salamander Grand
Piano (CC BY 3.0), sitting a minor third apart
and pitched at most a semitone to reach the notes between them. They live in public/piano, about
500 KB, and decode in the background on load rather than waiting for a click. Until they land, and if
they never do, a synthesised voice covers every note, so the drill still works offline and on a
browser that refuses the fetch. See public/piano/NOTICE.md.
Web MIDI only exists in Chromium (Chrome, Edge, Arc, Brave). Firefox and Safari ship no
navigator.requestMIDIAccess, so there the on-screen keyboard is the input — click the keys, it
behaves identically. The app tells the three failure modes apart rather than lumping them into one
message: no API, permission refused, and no device connected each say something different.
Chromium prompts for MIDI permission on first use. If you refuse it, re-allow it in the site
settings next to the address bar and reload.
Everything compares sets of pitch classes, never raw MIDI notes, so octave, order and inversion are
all irrelevant: C-E-G, G-C-E and E-G-C validate C major identically, and doubling a note changes
nothing.
Inversion drills are the one exception, and only a partial one. They still compare the same set,
then additionally check the lowest note you played. Everything above the bass stays as free as it
ever was.
pnpm install
pnpm dev
pnpm test runs the theory suite, pnpm lint and pnpm typecheck the rest.
Push it and import the repo on Vercel. Nuxt’s zero-config Vercel preset handles the build, there is
no vercel.json and there should not be one: any Permissions-Policy header would kill MIDI in
production. History lives in localStorage, so nothing is stored server-side and stats are per
browser.