Oh, come on guys--can anyone say that the Bard as a class is threatening? How often do you actually USE the perform skill? This haggling over whether the Perform skill lets you use a Harp better than a Harmonica... Yeah, I can unequivocally say that learning one instrument makes it exponentially easier to learn others to a similar degree of competence. That's what the vast majority of Music Majors have to learn: they don't just learn one instrument, they learn a whole handful, and keep learning as they go on, at a faster rate, because the more they know as a whole the better they can play each individual instrument. It's the same with acting: actors have a tendency to be better public speakers (Johnny Dep is an exception, not the norm). It's perfectly logical that a single number represents each and every genre's competence because a person who knows Tap dance will more easily learn Modern Jazz Dance, and be better at it faster.
That said, I play a Bard, and I have NEVER been in a situation where that was important. It's terribly sad, but I think I have used my perform skill...well, I guess I have NEVER used my perform skill outright to do anything but pump up an audience to get a circumstance bonus in my Gather Information skill.
Now, when you substitute your Perform skill check for a saving throw, which number would you use if you seperated all of your skill ranks into seperate performance types? Do you really think it's wise to nitpick a single skill to death, marginalizing it into uselessness? Doesn't the Bard have enough going against the class?
I dunno, I would leave it up to your DM. Don't count on WoTC to fix the problem in July--the whole class has been a study in "ambiguous rules" since it's been published, and none of the FAQ or errata have dealt with it...
--Coreyartus