Steely Dan co-founder Walter Becker has died at the age of 67.
The guitarist and bassist founded the jazz rock band with Donald Fagen in 1972 alongside guitarists Jeff "Skunk" Baxter and Denny Dias, drummer Jim Hodder and singer David Palmer.
Becker, who also provided backing vocals, and Fagen remained the core band members as other musicians and singers came and left.
His death was announced on Becker's official website, where a recent picture was posted next to a childhood photo along with the dates of his birth and death. No other details were given.
Fagen paid tribute to his friend as "hysterically funny" and promised to keep their music alive as long as he can.
In a statement to ABC News, he said: "Walter had a very rough childhood - I'll spare you the details. Luckily, he was smart as a whip, an excellent guitarist and a great songwriter.
"He was cynical about human nature, including his own, and hysterically funny. Like a lot of kids from fractured families, he had the knack of creative mimicry, reading people's hidden psychology and transforming what he saw into bubbly, incisive art.
"He used to write letters (never meant to be sent) in my wife Libby's singular voice that made the three of us collapse with laughter.
"His habits got the best of him by the end of the seventies, and we lost touch for a while. In the eighties, when I was putting together the NY Rock And Soul Review with Libby, we hooked up again, revived the Steely Dan concept and developed another terrific band.
"I intend to keep the music we created together alive as long as I can with the Steely Dan band."
In July Becker missed Steely Dan's Classic East and West concerts as he recovered from an unspecified ailment.
At the time Fagen told music magazine Billboard: "Walter's recovering from a procedure and hopefully he'll be fine very soon."
The group sold more than 40 million albums and were inducted into the Rock And Roll Hall Of Fame in 2001.
The band was reportedly named after a sex toy in the book Naked Lunch by William Burroughs.
The group split up in 1981 but reformed in 1993, and Becker also had a career as a solo artist.
They are slated to play shows in Dublin and London at the end of October.