The corpus callosum is a cluster of nerve fibers that connect the two hemispheres of the brain. On average, the corpus callosum of musicians is larger than that of non-musicians. Compared with adult non-musicians, adult musicians who began training around the age of 7 had a particularly significant difference in the size of the corpus callosum. 
Before musicians start training, their corpus callosum is no larger than that of non-musicians of the same age.
 music training, especially from childhood, can lead to some change in the structure of the brain.