[samibe]

I have my custom group set up as "Instrument". That allows sorting, filtering, selection of certain entries, and multiple entries in the field. Any choral music I add to my library gets added with "choir" along with the vocal complement, accompaniment instruments, and supplemental instruments. i.e. choir, SATB, piano, organ, bells.

I do wish that 'Instrument' was a default field in MSP so that the custom group could be used for other things. That or have a several custom groups to use.