Terry Melcher, Doris Day's son, and his friend Bruce Johnston used to do these Beach Boys rip-off numbers for Columbia Records. They're listed there as producers but they also sang on the records.
For a while they had a little Duo going on.
But they broke up and Terry decided to stay at Columbia and went on to produce The Byrds and Paul Revere and the Raiders for the rest of the 60 s.
While Bruce actually became a Beach Boy and started singing on the records before he got the publicity as a new member because of his Columbia contract.
Bruce is one of the outstanding voices on two of Brian Wilson's iconic songs--
"California Girls" and "God Only Knows".