Einstein and his violin

From The Myth of the Mozart Effect:

According to recent studies, the motor and auditory skills developed for musical performance may have a long-term influence on intelligence. In fact, brain mapping has revealed that professional musicians have more grey matter in their right auditory cortex than nonmusicians, as if practicing an instrument flexed a muscle in the brain. It seems increasingly likely that the long-term practice of playing music, rather than merely listening, can have the kind of impact suggested by the Mozart Effect. Einstein, after all, organized his mind by playing the violin, not listening to a recording.