Apparently some big music company filed a copyright claim on a video I posted because in the distance you can hear a muffled version of a song. It was filmed in a public place. SERIOUSLY?! #WTFU
While I agree the action is worthy of a WTF, as I understand it, they do have you on a technicality.
The fact that it was played in public would require those who played it to have paid a fee for the rights to do so. When you publish that on Youtube, you are also playing it to the public, but you haven't been given licence to do so - so you
are actually in breach of copyright. The fact that it's muffled and in the background and played by somebody else is irrelevant, even if it is of no importance to the clip. The fact that it is a performance which is covered by copyright means you have to watch out.
Whether it is a recording of a licenced performance is no different to someone playing it in their home and having a friend record it on their own device.
In fact, when thinking about it, you have probably done the wrong thing by just recording the performance ... but that's being really picky.