Proper noun
(historical) February 3rd, 1959, the day when American rock and roll musicians Buddy Holly, Ritchie Valens, and "The Big Bopper" J. P. Richardson were killed in a plane crash near Clear Lake, Iowa, together with pilot Roger Peterson.
(by extension) Any other day perceived in an extremely sad light, especially one in which a musician or musicians died, or in which negative consequences to the music industry were otherwise caused.
Frank Sinatra's death marked the Day the Music Died.
day the music died
Alternative letter-case form of Day the Music Died
I saw satan laughing with delight The day the music died. Don McLean
And the three men I admire most The Father, Son and the Holy Ghost They caught the last train for the coast The day the music died. Don McLean
I can't remember if I cried When I read about his widowed bride But something touched me deep inside The Day the Music Died. Don McLean