Stand

Stand is a shared music stand for my band. One person loads the charts, everyone opens the room on their phone and picks an instrument, and any phone's play button starts the chart scrolling on every phone together.

Sync is the hard part: play is scheduled two seconds ahead on the server clock (a "−2, −1" count-in), and every phone estimates its offset to that clock from round trips, so all the stands start within a few hundredths of a second of each other. Pause, seek, and song changes apply to everyone.

On top of the stand: colour chord charts timed to the recording and shown as blocks that light up on the beat; a drum part that plays as a highway, like a rhythm game; and a Sing mode that listens through the phone's mic, shows the tune coming as bars at their pitch, and scores each note as in tune, sharp, or flat. Pitch detection runs on the phone itself (Web Audio + the McLeod pitch method) — the sound never leaves the device.