John T. Siomos, or John Headley-Down as he was credited sometimes, was an American drummer who performed with Todd Rundgren, Mitch Ryder and the Detroit Wheels, Rick Derringer, Carly Simon, Mark "Moogy" Klingman, Buzzy Linhart and Frampton's Camel. He is credited for co-writing and performance on Peter Frampton albums.

In 1972, Peter Frampton was in a pinch to find a new drummer. Producer Eddie Kramer recommended three. Siomos was the only one to answer their phone. He had previously recorded with Todd Rundgren and was on the verge of joining Rundgren's band (Utopia). Upon an audition, Siomos was hired. But almost jeopardized it by being a "no-show" for the new album sessions. Resulting in Frampton playing drums on two tracks on the 1973 "Frampton's Camel" album.

It later came to light that Siomos had a heroin addiction problem during his tenure in Frampton's band. Yet, Frampton and Rundgren praise him as one of the very best drummers ever. Saying he played with a unique "feel" that many don't possess.

Little more is known about him, and there aren't many photos of him as well. According to Wikipedia, one of his jobs outside music was that of emergency medical technician. Siomos died in Brooklyn of undisclosed causes on January 16, 2004.