there's a lot of recorded snippets of live music on my profile; for me, it actually doesn't have anything to do with them, it's just a part of the vlog. i've been questioned a few times and i'm just totally transparent: what i'm doing has nothing to do with recording them and everything to do with documenting me. they're not any more important or special than the seagull i filmed last night when i was smoking a joint in the park. so, i go to a lot of concerts and i try to take one song from each band i'm there to see. but, i'm the topic, not them.
i think that logic transfers over to really anybody that's taking a song or two for personal use, whatever it happens to be. but, as mentioned, there's a point where it's not reasonable. it's all about discretion around a concept of reasonable behaviour.