McKenzie suffered from Guillain-Barre Syndrome, an ailment of the nervous system, and was hospitalized several times in the last two years of his life.
The song "San Francisco" was composed by John Phillips of The Mamas and the Papas.
McKenzie was born in Jacksonville, Florida, and raised in North Carolina and Virginia. In the 1950s he teamed up with Phillips, son of one of his mother's friends.
McKenzie sang with Tim Rose in The Singing Strings, and then with Phillips, Mike Boran and Bill Clearly in The Abstracts, which later in New York became The Smoothies.
In 1961 Phillips and McKenzie joined forces with Dick Weissman in The Journeymen band, which recorded three albums with Capitol Records.
Years later, when Phillips was already part of The Mamas and the Papas, he composed and co-produced for McKenzie "San Francisco (Be Sure To Wear Flowers In Your Hair)".
McKenzie also co-wrote the 1988 Beach Boys hit "Kokomo".