PL - I think I understand and appreciate where you are coming from, but IMO (as someone who also taught teenagers for a time) if you only feed teenagers what they WANT to hear, it is less likely that they will be receptive to what they SHOULD hear (i.e., proper terminology). They want to be adults - so treat them as adults.

But your post assumes that "song" is not proper and correspondingly that words can't change meaning.

It's not as though teens want to hear "song", it's just the word they know. I think far more than teens that use this word for any piece of music.