The long one

A track with an artist and no audio, which is the ordinary state of a music page that somebody is still filling in.

When a file does arrive, its waveform is computed once and stored as a few hundred numbers on the document — hidden from the editor for the same reason a snapped map route is, because a metadata chip would stringify the lot on the main thread. The scrubber draws from those peaks rather than decoding the audio again on every page load.