Man I agree with Lord GOD completely on this. At higher levels of bard skills, your gains will slow from an infantile crawl to something more akin to a snail moving in reverse if you keep letting music increase.
Thankfully if you decide to buy a few points in something to knock music back down to 90, it is a very easily trained skill. Once you're finished using masteries to train your other bard skills, you simply need to spam click on any instrument. (non-exceptional? Not sure if this makes a difference with music)
Active use of the music skill itself by playing an instrument doesn't diminish charges, and only has the tiniest of cooldowns. You can spam it 2 or 3 more times before the music sound effect is even finished playing.