If you are interested, visit the website I provided below.
This is a big name in the field. However, I want to remind you that music is not the only one of the stimuli for child's brain development. Any other stimulation could do the job.
His early finding that mouse living in a stimulation-rich environment has more synapses (connections between neurons) support the thought that learning piano or other music instruments will benefit kid's brain development. But nobody can say this is the only way.