the (finite?) instrument

A notion that turned up in the very first class this semester was that (experimental) improvisation broke boundaries, and that one of the boundaries in need of breaking was that of the instrument.
I’m interested in (and find problematic) this idea of the finite instrument, or of the instrument which needs to be (heroically) overcome. I think some of the students were confusing two separate ways in which the instrument might be bound and finite. An instrument may be finite in the sense that there are, perhaps, fixed channels, or specific protocols, for interfacing with it. It does not, however, follow that this restriction leads to finite possibilities in the aggregate behavior of the system or the resultant music.
There may only be six strings, twenty-plus frets and two hands, but I can’t begin to estimate the possibilities in the guitar-guitarist combination.