perhaps 4 or so, i don't really recall. i had an electronic toy piano, just something i could mess with. i believe i first played the concertina piano at the age of 6, wasn't great at it, but learned a simple song for the keyboard by 7 thanks to my dad, and played it at a family reunion musician gig when i was 9. "Black Magic Woman / Gypsy Queen" would be the name(s) of the song(s), by Santana.
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your age when you first did paid work.