This band was a true one-hit wonder. Originally from Florida, Blues Image moved to Los Angeles in 1969 and released one album before 1970’s “Open,” which included their only hit, written by guitarist/vocalist Mike Pinera and keyboard player Skip Konte. It reached No. 4 and was one of the songs of the summer that year. But the band broke up the next year, most of its members leaving to join other bands. Most of the tasteful guitar work is by Kent Henry, later of Steppenwolf. Mike Pinera, who plays the solo on the outro, left the band while the album was being recorded to join Iron Butterfly.
https://www.youtube.com/watch?v=qAnGe40-o9Q
I remember the summer this song was a hit, and part of the appeal was trying to figure out the inspiration for the 73 men who sailed up from the San Francisco Bay. Was this based on a true story? Not quite. Konte, who wrote the song with Pinera, revealed years later that 73 was the number of keys on his Fender Rhodes electric piano, so he started with that. He liked the rhythm of the first line, and the song “just sort of wrote itself from there.”