Well I don't know how this got by me. Los Angeles-based artist/curator Doug Harvey organized "The Patter Of Tiny Brains," an exhibition of audio of or by children, for the phone-based art gallery, 323 Projects.
Basically, you can call up the gallery, (323)843-4652 or (323)TIE-IN-LA, any time, day or night, and listen to the show. The kids run from ages zero to about 13, and the recordings date from between yesterday and maybe the early 1970s, though one piece I heard definitely sounded like the 50s.
I just called, and listened to, among other things, a pre-verbal baby laughing his head off; some 7yo or so boys self-consciously announcing themselves to themselves before devolving into poo jokes; trippy disco tracks with faint kid vocals; and a weird spoken word song where Uncle Tommy explains that good girls don't get spanked, so maybe you're not a good girl after all.
You can skip tracks, and I really wanted to find THUUNDERBOY!, the 1971 turntable performance by Ted, the 2yo son of avant garde filmmaker Tony Conrad. But for the life of me, I couldn't match up a single recording to the descriptions on the contributors list.
Still, it's pretty awesome. Will call back.