Conduct a classical tune with one finger. The sheet is the score and your finger is the clock: every stride of line you draw sounds the next note of the piece. Fast is a fast tempo, standing still is silence, and a long note wants more line than a short one, so the rhythm comes out of your hand while the proportions stay the composer's.

Where you draw matters too. The top quarter of the sheet plays an octave up, the bottom quarter an octave down, and the higher your finger the brighter the tone. The trail stays: a line, with a dot per note lit by its pitch.

Twelve pieces, baked in as notes and read out of the Mutopia engravings, not from memory: Beethoven's Ode to Joy (the whole theme, twice, the second time an octave up) and Für Elise (the A part with its repeats, the F major part and the first phrase back), Mozart's Eine kleine Nachtmusik (violin I, the first movement through the second theme), Bach's Minuet in G (all 32 bars with the repeats), Greensleeves (verse and refrain, twice), Satie's Gymnopédie No. 1 (whole) and Gnossienne No. 1 (whole, in the order the score plays it), Happy Birthday and Frère Jacques (twice, the second time an octave up — Frère Jacques is a canon, so the second voice is you again), Vivaldi's Spring (the solo violin, bars 1–43, the birdsong bars shortened to a handful of B's), Chopin's Nocturne Op. 9 No. 2 (the first sixteen bars) and Rimsky-Korsakov's Flight of the Bumblebee (the clarinet part of a Finale engraving at concert pitch, bars 1–46, the opening through its first return — all sixteenths, so draw fast). Grace notes, trills, turns and mordents are left out, held notes are capped at four beats and the shortest at a quarter beat. Every note is a fresh oscillator, gone after its envelope: nothing sampled, nothing fetched, nothing kept but your settings in this browser.

Play plays back what you just did: the line grows again at the speed you drew it and the notes fall where they fell — with whatever voice is chosen now, so the same drawing can be heard as organ or music box. Drawing during a replay stops it and starts a new take; clear throws the take away. Record and then play is how you make a film of a piece.

Save hands you the sheet as a PNG at twice the size, with the piece's name on it. Record asks the browser to record this tab — screen and sound — into one video file (mp4 where the browser can, webm elsewhere); baton's own sound is mixed in even when the browser hands over a silent picture. The file is only offered for download, never sent anywhere.

What it does not do: a melody only, no chords and no accompaniment; an iPhone with the mute switch on stays silent, as it does for every web page; and the tune is only as good as your line.