I uploaded the Pedro Sanchez vals above (i.e., below), and almost immediately got an email from YouTube to tell me that the music track is 'owned or licensed by WMG'. They tell me that 'for the time being' I needn't do anything. They have added a link to iTunes, where you can purchase the track as a download.
I thought this had happened because I identified the music in the writing, so I changed the wording, but then I noticed that the same thing has happened to another tango I uploaded two years ago. I didn't know what the music was, so I didn't identify it in writing but it's been spotted, so now I know what the track is, and which orquesta. Their software obviously crawls around YouTube's vast servers, emitting unpleasant odours every time it recognises a piece of music. I've noticed elsewhere that music tracks have simply been removed from videos because they violate copyright, so I guess I'm lucky '...for the time being': they can change their policy.
If all the owners of music start to do this we have a really serious problem. I've learned a great deal from watching tango on YouTube, and enjoyed fragments of a lot of other dance, but a dance without music, particularly an improvised tango, is close to meaningless. The reaction seems particularly harsh when the music is not taken digitally from a CD, but is recorded from a loudspeaker in another room, with the sounds of traffic, wind, birds and a sizzling barbecue mixed in. The answer, I guess: YouTube Downloader is simple and free, and there's a Mac version too.
I hope this doesn't go too far, as almost anything I watch on YouTube probably involves copyright material, often in low quality and in bits and pieces, but useful. (I tend not to watch home-made videos of teenage birthday parties, or of how to take a clock apart.) If anyone else has had problems with this, or knows anything about it, I'd be interested to hear. I believe it's very recent, so we may be at the beginning of a big change in the way we can use YouTube. It would be very sad if it reverts to being a storage for home-made videos of how to dismantle clocks.