Recent studies have shown differences between several structures in the brains of professional level musicians and non-musicians. Professional musicians form an ideal group to study changes in the human brain due to the unique abilities required of them. Since many musicians begin training at a young age, it is assumed that these differences are attributable to intense, early experience brought on by the cognitive and motor demands of music training. However, it remains to be seen whether these structural differences are due to changes brought on by experience or preexisting ones which draw children to music lessons. Using magnetic resonance images, I compared the size of the corpus callosums in two groups of children who ranged between the ages of five and seven, one just beginning music lessons and another not beginning music lessons. I also compared the groups in terms of their performance on a finger tapping test for differences in speed and accuracy. A second set of comparisons of callosal size was conducted between nine-to-eleven-year-olds who had been taking music lessons for at least a year and those who had not. Differences in the five-to-seven-year-olds were seen in the anterior corpus callosum corrected for brain volume between the musician and non-musician groups. Differences in accuracy of finger tapping were seen between the musicians and non musicians, as well as between those in the musician group who had received less than sixteen or twenty-five weeks of training versus those who had received less. These findings indicate that while musicians start out with at least one slightly larger measure of corpus callosum size, differences in finger skill tend to develop slowly.