He recorded for Disques Vogue and Columbia Records, appeared in films including Asphalte and The Devil's Brigade and voiced one of the Merry Men in Shrek.
The poet, singer and writer died of heart failure on Tuesday morning (April 2) in Detroit.
McMartin guided the career of Hoodoo Gurus for four decades and established the professional framework for the music management community.
The Grammy-winning musician performed frequently at La Scala opera house in Milan.
The Oxnard, Calif., native's manager, Jack Sills, announced the news on Instagram.
The rare student of Vladimir Horowitz, he made a dazzling Carnegie Hall debut at age 20 and performed major concertos from Chopin, Mozart, Rachmaninoff, Liszt and Prokofiev.
The British singer-songwriter was undergoing cancer treatments.
"The Band will miss our friend, brother, and band mate Anthony 'Baby Gap' Walker," reads a post. "Gone too soon. We will never forget you!!!"
Boyd joined the Academy as an executive secretary in 1968, as the organization's first paid employee, and rose through the ranks.
"It brought him great joy to know, that for decades, his music touched so many and will be his lasting legacy," his wife Amy Carmen writes.
