Chris Squire, the bassist, backing vocalist, and co-founder of English prog-rock legends Yes, died this afternoon while receiving treatment for acute erythroid leukemia in his adopted hometown of Phoenix, Arizona, less than six weeks after his initial diagnosis. The news was first announced by current keyboardist Geoff Downes, who tweeted, “Utterly devastated beyond words to have to report the sad news of the passing of my dear friend, bandmate and inspiration Chris Squire.” He was 67.

Squire grew up in the suburbs of London, singing in a church choir as a young boy. He played in a number of bands in the 1960s, including the Selfs, the Syn, and Mabel Greer’s Toyshop, which introduced him to guitarist Peter Banks and vocalist Jon Anderson. They formed Yes in 1968 along with keyboardist Tony Kaye and drummer Bill Bruford, quickly making a name for themselves on the London club circuit and releasing their self-titled debut album in 1969.

Squire, who also went by the nickname “Fish,” was known for his signature melodic Rickenbacker bass sound. He co-wrote much of the band’s catalog, and he was the only constant presence in a perpetually shifting lineup. Read an official statement from the band and watch some of Squire’s performances below, and check out our ranking of Yes’ discography here.

It’s with the heaviest of hearts and unbearable sadness that we must inform you of the passing of our dear friend and Yes co-founder, Chris Squire. Chris peacefully passed away last night in Phoenix Arizona, in the arms of his loving wife Scotty.

For the entirety of Yes’ existence, Chris was the band’s linchpin and, in so many ways, the glue that held it together over all these years. Because of his phenomenal bass-playing prowess, Chris influenced countless bassists around the world, including many of today’s well-known artists. Chris was also a fantastic songwriter, having written and co-written much of Yes’ most endearing music, as well as his solo album, Fish Out of Water.

Outside of Yes, Chris was a loving husband to Scotty and father to Carmen, Chandrika, Camille, Cameron, and Xilan. With his gentle, easy-going nature, Chris was a great friend of many … including each of us. But he wasn’t merely our friend: he was also part of our family and we shall forever love and miss him.