Tone colour is the element I'm playing around with in this piece. Also the fact that the acoustic guitar often has problems holding its own with a drum kit and a good strong bass sound particularly if you don't amplify the guitar. 

Timbre is probably a better description for the piece if perhaps a bit self conscious. Anyway, this was put together during a quiet afternoon at school - it was meant to be much more complex - but less is more for this one - I think