Leslie West, known best as the frontman and guitarist for rock band Mountain, died on Tuesday (Dec. 22). He was 75 years old.

His brother, Larry West Weinstein, shared news on Facebook of the star’s declining health on Sunday, according to Variety. “I am asking for all your prayers,” he wrote. “Jenni [Leslie’s wife] is by his side in Florida but it’s not looking good. Thanks Jenni, he wouldn’t have made it this far without you. His heart gave out and he’s on a ventilator. May not make it through the night.”

Mountain formed on Long Island, New York in 1969 and released three albums before they broke up in 1972 — though they’ve reunited frequently since and released a number of other projects including 1974’s Avalanche, 1985’s Go for Your Life, 1996’s Man’s World, 2002’s Mystic Fire and 2007’s Masters of War. The group notably performed at Woodstock in 1969.

Their best-known song, “Mississippi Queen,” peaked at No. 27 on the Billboard Hot 100 songs chart in 1970.

West was inducted in to the Long Island Music Hall of Fame in 2006, and appeared on dozens of other recordings from a vast universe of artists. Samples of his performances lived a secondary life on the masters of hip-hop and rap stars.