Greg Lake, the prog-rock progenitor who co-founded King Crimson and Emerson, Lake and Palmer, died Wednesday after a lengthy battle with cancer. He was 69.

As much as other instrumentalists created the sounds that defined his bands— Robert Fripp’s guitar in Crimson and Emerson’s keyboards in ELP—Lake quickly became one of the most identifiable singers in then-nascent progressive rock.

A guitarist, bassist and songwriter, he sang epic pieces such as “The Court of the Crimson King” and “21st Century Schizoid Man” in King Crimson. He was the balladeer in ELP, performing softer acoustic songs such as “Lucky Man,” “From the Beginning” and “Still…You Turn Me On” that altered the pacing on ELP albums full of lengthy, uptempo pieces.

As pre-teens, Lake and Fripp took lessons from the same teacher

As a youth, Lake played folk and classical music, and as a teenager played in a series of rock bands. He learned guitar in the English seaside town of Bournemouth where one of his fellow students was Fripp. In 1968, Lake was leaving The Gods just as Fripp was bailing on Giles, Giles and Fripp, leading to the formation of King Crimson.

The initial lineup was together for only a year and Lake appeared only on the first two Crimson LPs. Keith Emerson’s manager, Tony Stratton-Smith, inquired if Lake would be interested in joining his client, whose band The Nice was breaking up. They recruited Atomic Rooster drummer Carl Palmer and formed one of rock’s early “super groups.”

Ahmet Ertegun signed them to Atlantic after seeing them perform at the Isle of Wight Festival in August 1970. Emerson Lake & Palmer was released in November, peaking at #4.

They were an instant hit with the debut album, which included “Lucky Man” which quickly gained traction at radio. All of their studio albums except their final one, Love Beach, and a live three-LP set landed in the Top 20 in the U.S. and the U.K. On tour, they were famous for hauling 40 tons of equipment to packed arenas and stadiums throughout the world.

In 1975, Lake had a solo hit with “I Believe in father Christmas,” which has become a holiday standard at classic rock stations.

After ELP broke up in 1979, Lake recorded solo albums, toured as the lead singer in Asia, went out with Ringo Starr and his All-Starrs in 2001, and reunited with Emerson in Emerson, Lake & Powell. ELP would record and tour on an on-again, off-again basis for decades; in July 2010, the trio performed a 40th anniversary concert in London.