To be honest, I don't always listen to music when diaboloing. I go to two juggling clubs, at the first we share the halls with cheerleaders so I have spent the last 6 mondays listening to their music (and slowly going insane), the other club doesn't tend to have any music. When music is played it's hard to please everybody
I find that the best music for me to diabolo too isn't always the music I like to play at other times. I find that if the music is too fast I tend to rush and things go to pieces. Basically I like something with a bit of a beat and the kind of tune that is predictable (so I can time certain tricks for when I hit a certain part of the tune).
One thing I did when trying to find music to perform to was listening to a radio (whilst diaboloing) and switching between stations untill I found a style or song that grabbed me. It gave me a better idea of what was available rather than just relying on my own cd collection.
I suppose going through the Internet radio stations might give you a wider choice than you get with normal radio. Then I suppose burning of a compilation of likely tunes or even getiing hold of some 'best of' cds' might be usefull.