One of the problems with listening to music on a bike, is, if you use headphones/helmet speakers.....most portable devices don't have enough audio output to overcome wind and road noise.
Helmet speakers help, but it's still a little borderline.
Earphones can be used, but unless you get custom made ones, can be uncomfortable under the helmet, or inefficient.
I played with using a walkman, and several 2 way radios on the bike 4-5 years ago.
Audio level, and general comfort were problems.
If you use helmet speakers, you'll end up with a wire dangling from your helmet you need to live with, and connect/disconnect, depending on what it's hooked up to when you get on/off the bike.
There is a FM stereo mounted in a tankbag, with external speakers....called a 'Bag of Tunes'.
Then you get to annoy the world as you blast down the road listening to
Slim Whitman......
It would be easy enough to rig up an old tankbag, with a modest car stereo, if you want to go that route.