Hey there, the difference is really to do with how formal you want to sound. "Rhythmic song" already sounds quite formal to the point of I would consider changing it depending on the context. Music being a large part of culture, it's usually subject to a lot more slang and so unless you're writing this in a very formal setting I would consider saying or writing something more along this lines of "kicked off this morning with a *insert local slang for song eg. Banger, tune (I'm Australian so that's what I'm basing it off)*.
If you're writing a story you might prefer "the mood was set by the rhythmic drums and catchy melody"...and so on.
Rhythmic song sounds a little clunky is all but I'm possibly being too pedantic.