@startid vs. @tstamp vs. @plist on spanners

[th-we]

This is related to #75.

I have a WIP branch that is intended to add @startid, @endid and @plist to all "spanners", following the voice numbers 0-4 (0 meaning "add @plist reference to notes from all layers").

I'm wondering in what situations @startid/@endid should actually be added in addition to @tstamp/@tstamp2/@plist. The situations I'm wondering about are:

• when lines like hairpins start/end between notes, i.e. are not really attached to notes
• for multi-voice lines, there might be multiple start/end notes - picking one would be arbitrary and potentially misleading

I therefore want to omit the @startid/@endid whenever there is no 100% clarity. I'm not 100% sure, though, because @startid/@endid might be useful for applications that can't/don't want to parse @tstamp/@tstamp2.