Syd Barrett wrote “See Emily Play” in the wake of Games for May, the band's concert at Queen Elizabeth Hall on May 12, 1967. It was one of the first major events of the London psychedelic underground built around a full quadraphonic PA system, with sound panned around the room and bubbles drifting over the audience. EMI and producer Norman Smith wanted a follow-up single to “Arnold Layne” that could climb higher than its predecessor had. Abbey Road's equipment could not reproduce the effect Barrett and the band were chasing, so they booked time at Sound Techniques, the small independent studio in Chelsea where they had cut their earliest demos.

The identity of Emily has never been settled. Barrett told one story about a young girl he saw sleeping in the woods near Cambridge. The band's own publicity at the time offered a different account that members later admitted was simply invented for the press. Some who were close to the London UFO Club scene have pointed to the Honourable Emily Young, a regular presence at the band's early gigs who went on to become a respected sculptor. Barrett's childhood friend Libby Gausden has said he once told her, half joking, that he would name a future daughter Emily. None of these versions cancels out the others. The song was built to hold a private joke that nobody outside the band was meant to fully solve.

The record's oddities are part of its appeal. The piano break midway through was played slowly by Rick Wright and then sped up in the mix, giving it a brittle, toylike quality that mirrors the lyric's dreamlike drift. Tape effects run backward under the verses. The original four-track masters were reportedly wiped or lost not long after release, which means “See Emily Play” has never circulated in a true stereo mix. Every reissue since has had to work around that absence in one way or another.

The single reached number six on the UK chart and pushed the band onto “Top of the Pops” three times in July 1967, a level of pop exposure none of them, least of all Barrett, had been built for. He reportedly bristled at the demand to lip-sync and repeat the same performance week after week, asking why John Lennon never had to do this. The BBC later wiped the broadcast tapes of those appearances, and only a partial recovery surfaced in 2009. David Gilmour, visiting the sessions before he had officially joined the band, watched Barrett come apart in real time under the pressure of sudden chart success.

Barrett left Pink Floyd in early 1968, less than a year after the single's release. The band carried the memory of him forward for decades. Rick Wright closed “Shine On You Crazy Diamond” with a Minimoog line that quotes “See Emily Play,” folding the song directly into the album built to mourn what Barrett had become. “See Emily Play” was released June 16, 1967. Today is its 59th anniversary.