A press release confirmed McDonald's passing, explaining that he died Wednesday at his home in New York City "surrounded by his family."
McDonald had been working as a session musician in his native England when he co-founded King Crimson in 1968 with Robert Fripp, Michael Giles, Greg Lake and lyricist Peter Sinfield.
McDonald's versatility is on full display on the outfit's groundbreaking 1969 debut album, In the Court of the Crimson King, where he's credited with recording saxophone, flute, clarinet, Mellotron, harpsichord, piano, organ, vibraphone, backing vocals and production.
After King Crimson's first U.S. tour, to Fripp's dismay, McDonald left the band to pursue other projects. He can be seen briefly in the trailer for the new King Crimson documentary, apologizing to Fripp for "breaking [his] heart."
In 1976, he was again part of something extraordinary when he joined Foreigner's founding unit of Mick Jones, Lou Gramm, Dennis Elliott, Al Greenwood and Ed Gagliardi to provide additional rhythm guitars, woodwinds and keyboards.
This time McDonald stuck around long enough to enjoy the band's success, which including three multi-platinum albums, Foreigner, Double Vision and Head Games, before his departure in 1980.
McDonald later reunited with Foreigner during the band's retrospective shows in 2017 and 2018.