Im not absolutley positive but I've heard or guessed that a midi is nothing more than a script that tells what your computer to play.
So in the sense, you did not download the music.... its your PC that emulates the music, and the midi file is like the notes.
midi is old school, its made up of tones from a synthesizer. believe this is called structured audio; where no voices are allowed, just the synthesized sound. the end result is a tiny file size. format is pretty much outdated now and only used f/web pgs and phones.
yeah the same midi song will sound different on another comuter with a different sound card. it is up to midi software or sound card to render each piece of sound.
well i found it randomly on my computer and im at a loss to find crazy irish songs on the net but there are awesoem ones at www.mididb.com like linkin park and blink182 and just search google for MIDI. IF i find crazy ones ill post them on my site just for you A_Zip1