Glen was never a full time member of the Beach Boys but he did a 4 month fill in for Brian Wilson during a tour in the mid sixties. Glen was a long time member of a band of session musicians known as the Wrecking Crew who accompanied many well known artistes in the Sixties. He did play guitar on Pet Sounds but didn't receive a mention on the album credits, he also played on Frank Sinatra's Strangers In The Night Album and several of Phil Spector's studio hits inc. You've Lost That Loving Feeling.

Here's another song from the covers album he did in 2009, a Jackson Browne track this time.

https://www.youtube.com/watch?v=fiJEHeUqCEE