It just takes a bit of practice ... I don't wear earphones while riding, but I did have one a few times...
My driving instructor had us (we were a group of about 4 students) each wear a receiver, and he had a microphone in his helmet and transmitter in his pocket - he would ride ahead to demonstrate something, then behind us to give each of us tips, and tell us which way to turn at the next intersection.
When I took the "little" motorcycle license test (back then, it allowed me to ride a 125cc / 15hp), the inspector had me wear a backpack with the recevier in it, and the plug in one ear - he followed in a car, giving instructions and watching my riding technique.
For the "big" license (unlimited HP), the inspector rides pillion, giving instructions by tapping on your shoulder and giving hand signals.