He was the bassist of the Turtles for a short period of time and the producer of some of the Monkees biggest hits, including "Daydream Believer" and "Pleasant Valley Sunday".

Douglas was raised in Hawaii and began his musical career with a folk group he formed in high school, "The Wilcox Three", modeled after The Kingston Trio.

The group dissolved and Douglas, along with Cyrus Faryar and noted rock photographer Henry Diltz, formed the Modern Folk Quartet (along with musician Jerry Yester) in Los Angeles.

They also appeared as themselves in a nightclub scene for the Warner Bros. movie Palm Springs Weekend, starring Connie Stevens and Troy Donahue (1963).

Douglas played bass and did the arrangement that was recorded, and it became a huge hit for The Turtles, ousting the Beatles' "Penny Lane" from the #1 single position on the American pop charts.

[2] Seeing the Turtles perform at Hollywood's Whisky a Go Go in early 1967, the Monkees' Michael Nesmith approached Douglas and asked if he would like to become the new producer for the band, who were tired of the "manufactured" recording setup they were accustomed to.

Nesmith, who had produced album tracks for the group, but had little influence with their label Colgems Records, assured him, "Don't worry; if you're willing to quit The Turtles, I'll show you everything you need to do.

Recorded over six steady weeks of sessions at the RCA Studios in Hollywood, Headquarters was the first album to feature the Monkees playing on every track.

[2][3] No singles from Headquarters were issued in the United States, but a non-album song from the same sessions, "The Girl I Knew Somewhere", reached the top 40 as a B-side.

Douglas was demonstrating the song for vocalists Howard Kaylan and Mark Volman, on an organ whose bellows was broken, requiring him to play it slowly.

In 1986, a Monkees reunion tour reawakened interest in the band, and Rhino Records reissued all their original albums, including their work with Douglas.