On modes doable on diatonic instruments: my axe of choice is the diatonic harmonica. If I'm playing a D harp I can play tunes in Ionian (D major), Mixolydian ("key of A with flatted 7th"), two "minor keys" in Dorian and Aeolian modes (tell the guitar men that they're E minor and B minor respectively and they're happy) and Lydian ("G Major with sharpened 4th"). I won't bother repeating the exercise for a G harp but you get the idea. That covers most tunes in Irish traditional music, though other modes are available. Lydian doesn't really cut it because those tunes, via missing notes are also (mostly) playable in Ionian on a different-key harp. Cronin's hornpipe is one such. It's a fun topic, seemingly not well grasped by Pseudonymous, but admittedly a bit of a diversion. I'm not much of a scholar on the origins of modal music but I suppose "our" kind of music was much-influenced by the early church modes - and the fact that modal tunes are often better adapted to simpler instruments that weren't too adept at playing sharps and flats.