Really nice! Props for Svelte.
A one minute doodle: https://music-grid.surge.sh/#41-512-320-2597-840-64-512-1189...
Would be nice if it did `history.replace` instead of push, it currently nukes your back button. There is also something off, maybe a 4-note limit per row? I couldn't quite put my finger on it but some high notes seem to not come out.