Legion’s connection to the ‘70s progressive and psychedelic band Pink Floyd is apparent from the first episode when main character David Haller’s romantic interest, Syd Barrett, is introduced.

The real life Syd Barrett was Pink Floyd’s lead singer, guitar player and songwriter who was eventually kicked out of the band, and replaced by David Gilmour in April 1968. In Legion, Barrett is a patient at the same mental institution as Haller, and over the course of their stay, the two develop a relationship. The character is based on Barrett, but it goes much deeper than Hawley’s adoration for the singer or the band.

When showrunner Noah Hawley met with composer Jeff Russo to talk about how he wanted the show to sound, he was quick to point out Pink Floyd’s quintessential 1973 album, Dark Side of the Moon. Although the album was released in 1973 and used new recordings from 1971 and 1972, its concept was largely based on earlier live shows and recordings, which explored Barrett’s declining mental state.

“That album more than anything is really the soundscape of mental illness to some degree,” Hawley told a crowd gathered at New York Comic Con in 2016, as reported by Vanity Fair.

As we said in our review of the show, Legion is a series about mental illness. It uses the idea of Haller’s mutant abilities as a way to paint a picture of the isolation and alienation that accompanies not feeling normal. Hawley has spoken about this at length, reiterating he never wanted to make a superhero show as much as he needed to create a series about mental illness.

“The other aspect of this which is important, I think, to explore is that mental illness is no ... It’s a tragic condition that people have, and so I don’t want to use it for entertainment purposes,” Hawley told IGN.

Dark Side of the Moon is an album about a mental breakdown that occurred years of untreated depression that founder Barrett suffered from. There are university courses that explore the way Dark Side of the Moon handles mental illness, and Hawley wanted to use the album as a way to reinforce the values prevalent in those songs as they relate to the show.

There’s also the fact that Dark Side of the Moon is released in 1973, and Legion is a series full of 1970s aesthetic. Like the use of the album and Barrett’s name, it’s not accidental, and Hawley is very aware of the concept he’s trying to get across with the inclusion of Pink Floyd’s music.

Legion relies heavily on auditory and visual cues to hep gets its message across. For example, when Haller is experiencing a moment of psychosis, the screen becomes darker, and strange images flash across the screen. It’s paired with intense music and odd, conceptual cinematography to reiterate this isn’t a normal experience for Haller to be having.

As the series continues, Floyd’s album becomes much more obvious and the cues given to point out the music become much more notable. Although the real Syd Barrett was eventually booted from the band, his legacy continues to live on through the story behind Dark Side of the Moon and shows like Legion.

Legion airs Wednesday nights at 10 p.m. ET on FX.