Unless you just want to keep the song permanantly on your site, there is no need to embed a selection from You-tube.

Go to the You-tube site and find the song you are interested in. (There are always numerous versions of every song. Everybody and his brother thinks they need to give their separate opinion) Open up the song fully so that it plays on You-tube and not on someone's site or post. 

Then find the word "share"

Click share and copy the link that appears.

Post this directly into the Activity time line and it will appear as a link with full graphics showing.