[Zubersoft]

I used a generic term, but the field is meant to track charts vs lead sheets vs sheet music vs guitar tablature, etc. It's a little different than just instrument, as with piano you could have sheet music (with staves, note symbols, timing, etc) vs just chords and lyrics. It's really just to track how the music is captured, arranged and presented. Having said that, you can use the field for whatever you would like.

Mike