The many superb albums put together by space-opera rock pioneers Pink Floyd include The Wall, Animals and Darkside of the Moon. Then there’s Wish You Were Here, an album about conspicuous absence – metaphorically in regards to the music industry both literally, in regards to their bandmate Syd Barret, who was slipping away from them due to mental illness, and physically, with the album’s cover concealed by black wrap.

On this day, December 15, in 1975 Pink Floyd released Wish You Were Here, their ninth studio album, produced largely by frontman Roger Waters.

Opening the album is the lengthy, atmospheric track “Shine On You Crazy Diamond,” a tribute to Barret. “Remember when you were young, you shone like the sun,” Waters sang in memory of one of their own. “You reached for the secret too soon, you cried for the moon.”