Occasionally I like to compose, or at least do a sound sketch for my own projects. My instrument of choice is naturally the guitar, this is the instrument most people play, as it's easy to pick up and easy to access. Also similar to many basement guitar masters, I never learnt to read music or went to any training, instead I used tabs off the internet, my ear, and tips from friends and drunken hippies at those weekend parties where guitars inevitably end up. Regarding the Piano/keyboard - I am ham fisted. I play by ear and muscle memory and because of my limitations I play it very differently as I do the guitar.
Midi and Mod music interests me as an entire different animal. It is so limited by the size and sounds, often only 2 or 3 sounds are used, derived from simple adjustments or a square or sin wave. The pure tones are easily irritating, though if used right can be quite soothing. So again, the scores I've done with these are vastly different to any music I play or write on Guitar, even if they start out as guitar licks.