I see many children with autism in my clinic who are music savants. They have perfect pitch and can play a song on the keyboard after hearing it one time. The percentage of child with autism that have special music abilities is not know, but it is estimated that 10% of children with autism are savants.
In addition, many children with autism like music and we use it as a reinforcer in ABA programs. (Some kids with autism find music, and sounds in general aversive and cover their ears.) Neuroscientists tell us that infants are born with music preferences and even seem to enjoy music while still in the womb.
Some years back I had a 3 year-old girl come to my clinic with a diagnosis of autism. When I was taking her history her mother said she was not verbal, but she could sing. I then asked if she could follow directions. The mother said yes as long as she sang them. I then watched mother sing a direction and her daughter sang back her reply.
Tere is no music center in the brain. Pitch, loudness, and dimensions of music are in circuits of nerve cells, which are spread around in different parts of the brain. Why some children with autism have savant abilities is not even close to being understood.