Not really, you can have way more then nine if you like. It is a skill just like craft and profession. there are as many as you can think of. Just because you take 9 ranks in sing, does not mean your that good with flutes or drums or string interments if you can play them at all
But why not? The Bard is the master of instruments - if you really think that a Rogue shouldn't be both a good singer and a good lute player without investing tons of skill points, fine. But the Bard? He is the go-to-guy when it comes to music!
Instead of using his performance for something strange like Stealth or Sense Motive (I don't know if this would actually be possible

), why not just say "A Bard that takes ranks in Perform gets a rank for every Perform subcategory".
Could also be something for Artificers and Craft, if that was ever an issue or can ever be an issue in Pathfinder.
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Aside from all that - a Bard does not cover multiple roles. He covers a subset of them. If you really need someone in that role - be it the dedicated healer (that also deals with poisons and diseases, not just hit point damage), the dedicated trapsmith and lockpicker (that actually gets you through the Temple of Certain and Fatal Death), the dedicated meat shield (that can survive the full attack of an Ogre) or a fully-fledged spellcasters, he won't do it. He can just help you a little in ever aspect.
And often it is more important to have at least one of the guys that does the job really good then a guy that makes multile jobs mediocre. If you don't have a meat shield, you can still hope that the fully-fledged spellcaster blasts the opposition away before things turn ugly. Or that the dedicated healer keeps whoever stands in the front-line standing. Both need to take out their big "guns" in this scenario, of course. But they have the big guns. The Bard doesn't.
Three things that could make the Bard useful where usual:
- Social Skills
- Bardic Music (Reliable Buffing, even stacks with many other Buffs)
- Use Magic Device (unfortuntely not limited to the Bard and if you have a Wizard and a Cleric, not required.)