From Zappa Wiki Jawaka
Skip Diamond, name-checked on the cover of "Freak Out!" (1966) under the heading "These People Have Contributed Materially In Many Ways To Make Our Music What It Is. Please Do Not Hold It Against Them", was a musician. He features as a guest vocalist on Canned Heat's "Hallelujah" (1969) album, together with... Elliot Ingber (then from Fraternity Of Man) and Henry Vestine.