I've been listening to this recording of Handel's Messiah for a while now, and there was something about it that was irking me. It wasn't until I listened to it on earphones I discovered the full horror of the issue - Colin Davis is humming along to the music, and it is audible enough to be extremely irritating, even more so once you become aware. I can't actually listen to this version any more and am looking for a similarly recorded version as, humming aside, it is a fine version.
Others have mentioned the humming doesn't bother them, but for me, it's like having a stranger just behind your shoulder humming away whilst you're trying to focus on the actual music. I wouldn't put up with that - why would I put up with it on the actual recording?
In summary, a thoroughly fine but tainted recording.