Written by group members Felix Cavaliere and Eddie Brigati and with a lead vocal from Cavaliere, it is indeed a slow, relaxed groove, based on Cavaliere’s newfound interest in Afro-Cuban music. Instrumentation included a conga, a Cuban-influenced bass guitar line from ace session musician Chuck Rainey, and a harmonica part, performed first for the single version by New York session musician, Michael Weinstein, and later for the album version by Gene Cornish.
The result was fairly different from the Rascals’ white soul origins, enough so that Atlantic Records head Jerry Wexler did not want to release “Groovin'”. Cavaliere credits disc jockey Murray the K with intervening to encourage Atlantic to release the song. “To tell you the truth, they didn’t originally like the record because it had no drum on it,” admits Cavaliere. “We had just cut it, and he (Murray the K) came in the studio to say hello. After he heard the song, he said, ‘Man, this is a smash.’ So, when he later heard that Atlantic didn’t want to put it out, he went to see Jerry Wexler and said, ‘Are you crazy? This is a friggin’ #1 record.’ He was right, because it eventually became #1 for four straight weeks.”
The single became an instant hit in May 1967, bounding up the charts and then spending four weeks atop the Billboard pop singles chart. It was RIAA-certified a gold record on June 13, 1967. Showing it (and the group’s) crossover appeal, it also reached number 3 on the Billboard Black Songs chart chart. Finally, “Groovin'” was the only real hit the group ever had in the United Kingdom, reaching number 8 on the UK Singles Chart. (source Wikipedia)