[angularfocus]

I have the custom group named 'Instrument'. Each time I add a song to the library it gets assigned an instrument (or several) in the metadata. Then it's pretty easy to filter the library by instrument and find the songs I need. There are often multiples of different songs just because I might have multiple parts or versions for different instruments. 

I think song versioning is on the 'feature request' list that will better handle songs with multiple parts.

So I ended up thinking along the same lines, and since I don't typically use the "Key" field, I set all the Eb Parts to Eb. and the Bb parts to Bb, but I think I like your idea better.

Thanks!