When creating relationships with recordings. pointing to a certain time index (or a set of indexies) could come in handy to say things like:
The guitar solo at time index 2:24-2:45 was a guest performance by [artist]
The sample used at time index 1:23-4:56 & 7:12-8:34 was originaly published in the recording [recording] at time index 2:24-2:45
there already is a tagging standard for chapter marks within audio files and relatively common in podcasts and supportet by players.
the interface to add this might look painfully complicated