Who was the youngest person to perform at Woodstock?

1999 Woodstock:

Rubin began playing drums at the age of 8, when he discovered his Father's 1968 Silver Sparkle Ludwig drum kit set up in the garage. After three months of "toying" with the kit, he had taught himself to play and was jamming with his older brothers and by the age of 9 was ready to play for F.o.N., a band that eventually would do three stints on the Vans Warped Tour, where, in addition to playing with F.o.N. Ilan would fill-in on drums with bands such as NOFX. In 1999, F.o.N. opened Woodstock on the "Emerging Artist Stage" and, as a result, 11-year-old Ilan gained entry into the Guiness Book of World Records as the youngest musician to ever play on a Woodstock stage.

https://en.wikipedia.org/wiki/Ilan_Rubin

1969 Woodstock:
Henry Gross (April 1, 1951) of Sha Na Na is the youngest person, at age 18, to play on the main stage at the Woodstock Music & Art Fair in 1969.
https://en.wikipedia.org/wiki/Henry_Gross

Michael Shrieve was born July 6, 1949.
https://en.wikipedia.org/wiki/Michael_Shrieve