In 1967, David joined All Night Flight which later became the seminal 60’s psychedelic band, Frumious Bandersnatch. Frumious went on to be re-popularized in the '90s due to re-releases in Europe & the US.

“Frumious Bandersnatch was a psychedelic rock band in the late 1960s. The band was named after a character from the Lewis Carroll poem "Jabberwocky". Based in Berkeley, California, the band was active from 1967 to 1969. Their initial three-song EP produced a minor underground hit with the song "Hearts to Cry". A recording of their live work, titled A Young Man's Song, was released in 1996 by Big Beat (UK).

The band was formed across the bay from San Francisco in Contra Costa County, and changed personnel several times. Despite interest from several record companies, the band's only release was a three-song EP on their own label, pressed in a quantity of 1,000 and distributed locally.

Four members of Frumious Bandersnatch (Bobby Winkelman, Jack King, Ross Valory, and David Denny) became regular members of the Steve Miller Band. Valory, along with fellow Frumious Bandersnatch member George Tickner and manager Herbie Herbert, joined former Santana members Neal Schon and Gregg Rolie to form the band Journey in 1973.” – from Wikipedia (https://en.wikipedia.org/wiki/Frumious_Bandersnatch)