A read-only multitrack piano roll of a prepared timeline: ruler with cycle numbers, a section strip, pitched rows and a compact drum strip with General MIDI names. Sized by CSS (SVG paths stretched with preserveAspectRatio none, HTML labels in percent, no height prop); fit view samples to a note cap, detail view scrolls at 72px per cycle, culls to the viewport and follows the playhead unless the reader just scrolled or prefers reduced motion. The playhead is a leaf on a PlaybackClock moved by transform, so playback never re-renders the notes. Stale state dims it and says 'previous'. TimelineRollLegend adds swatches, mute/solo toggles (aria-pressed, 24px, Alt-click solo), channel numbers below 480px and an actions slot. Track colours are --uikit-track-1..8, starting at blue. Pure core beside it.
pnpm dlx shadcn@latest add "https://pluginui.com/r/core-timeline-roll.json"