Greetings, Patrick -
The tempo indications are just what they say. There's a lot of variation in tempo for the same tune at various sessions.This may not be a lot of help, but I would suggest three possibilities: 1) play the midi at a default or provisional tempo, decide whether it sounds right to you, then modify the tempo accordingly; 2) get a metronome with a beat input button, play or hum the tune the way you think it should go, then tap the metronome button at that pace to find the tempo; or 3) find a recording or an Irish session musician who will play the tune for you, and determine that tempo. No hard and fast rules, I'm afraid. I'd like to see the results when you're done. Incidentally, if you didn't know, all the O'Neill's tunes have been transcribed using ABC format and are freely available. Some of them may give tempos; I don't know. If you want to check them out, go to
http://trillian.mit.edu/~jc/cgi/abc/tunefindenter the tune name, and you can check out the ABC source file, a .jpg, a .png, and other formats. There will be *multiple* hits for each tune. If you want the O'Neill's, it will be identified by a number (I can't remember what the number is) all the way to the left of the entry.
Good luck,
Ralph