According to social media posts by friends and artists he worked with, Rieflin died after being diagnosed with cancer.
“Bill Rieflin flew from this world c. 18.50 Pacific, 18.50 UK,” King Crimson founder Robert Fripp wrote on Facebook, after receiving a phone call confirming Rieflin’s death.
He added, “Fly well, Brother Bill! My life is immeasurably richer for knowing you.”
Rieflin, a Seattle native, often served as a long-term auxiliary member, rather than a full-time part of any of the bands he became involved with.
Before leaving for a North American tour with King Crimson in 2017, Rieflin told Rolling Stone about his additional role on keys: “There was a question of four drums up front, which is still in the world of possibility. However, for this tour, I said, ‘Why don’t I just play keys?’ My skill level is not at the highest, but I’m capable.
“And so we said, ‘Yeah, sure, do that.’ Basically, I’ve made my own job after my other one was taken over by the exceptionally capable Jeremy Stacey. It’s unprecedented that I was brought back in, and unprecedented again that I now fill a completely different role.”
Variety noted an example of Rieflin's versatility as a musician was when he performed with Swans and also performed drums on Robbie Williams’s album, Take the Crown, around the same time.