Pink Floyd will reissue the mono mix of their second album A Saucerful of Secrets as a vinyl release for Record Store Day, April 13th.

Unlike the Beatles or Rolling Stones, the band transitioned to stereo fairly quickly, making this one of the rare albums in their catalog that originally came out in mono. The audio was remastered from the original 1968 mono mix by James Guthrie, Joel Plante and Bernie Grundman. The limited edition, 180-gram LP, housed in a “faithful reproduction” of the original sleeve, will come out on the group’s own Pink Floyd Records.

The record marks a pivotal moment in the band’s career, as it’s the only release to feature both founding guitarist, Syd Barrett, and his replacement, David Gilmour. As Barrett became unreliable at concerts, the group decided to eject him from the lineup. Barrett’s only songwriting offering to Saucerful is its closing track, “Jugband Blues,” for which he supplied the vocals; he also played guitar on “Remember a Day” and “Set the Controls for the Heart of the Sun.” He’d previously written the majority of Piper at the Gates of Dawn, which came out as a mono vinyl release on Record Store Day last year.

In a 2016 interview with Rolling Stone, Pink Floyd drummer Nick Mason said he’s changed his mind about the prevailing theories of why Barrett became erratic. For decades, rock mythology has suggested that Barrett had become an acid casualty and got lost in the music.

“Looking back on it, there’s no doubt that LSD exacerbated the state, but I think perhaps what was happening was Syd had realized he didn’t want to be in a rock band at all,” the drummer said. “He’d done that, decided it wasn’t really what he wanted to do and probably wanted to go back to art school, but he couldn’t find a way of getting out of it. Certainly, we couldn’t believe that anyone didn’t want to be in a rock band. So I think when he was messing around with the songs, like ‘Jugband Blues,’ I think he almost did it as a whim, thinking it would be another really peculiar thing, whereas actually I think the song has an extraordinary edge. I think what was going on was Syd really was trying to leave.”