I’ve mentioned before that both my parents loved music. Dad let my older brother Mike* play on the piano and I’m sure they played classical music records all the time when he was around. For a time Mike responded. I’m told he could hum entire movements from symphonies. By the time I came on the scene, Mike didn’t do that any more.
Mike never had speech, but somehow he could repeat tunes for a while. I understand that Mike still likes to listen to the radio even today in his group home. There are no reports that he sings along, though.
* Mike is autistic, low functioning and nonverbal