Translation:What music is this?
I also wrote song in order to check if it was accepted. I understand why it was not, there are a couple of issues:
- music can be used in a plural form in Chinese, but translating "那些音乐" to "those music" is definitely weird;
- instrumental music is not sung and thus a composition or a music piece would be preferable to a song when referring to this type of music (English Stack-Exchange example)...
In order to solve these, this phrase could be changed to "这是什么歌？" = "What song is this?" and another phrase could be added where the music (音乐) concept was introduced, e.g.: "谁写这些古典音乐？" = "Who wrote these classical music pieces?"
I wouldn't say it's "more common"; to me, at least, "what song" and "what music" mean different things. A song is a specific, discrete, relatively short piece of music, usually with lyrics. If I were asking about, for example, continuous instrumental background music, I wouldn't call it a "song"; I'd ask "What music is this?"