As breasts develop, they can become very sensitive to touch and, I believe, vibration. Sound waves can have a significant impact on the body. Remember standing in a room near those big speakers? You don't have to be that close. As a slight rub of a top against a nipple can cause a sensation, so can sound. The more you are involved in the music, especially playing or being involved in the activity, there is both a psychological and physical reaction. That is why listening to s certain song can cause the vc's, vaginal contractions! Either way, so much fun! Keep playing! Keep enjoying the ride! Hugs, Kelly