Syd Barrett — who was born Roger Keith Barrett — knew bass player Roger Waters from school. In 1962, Barrett had played in a band called Geoff Mott and the Mottoes, but he had left the band to move to London to study painting. So, when Waters needed a guitarist for his band The Tea Set, he tapped Barrett to fill the spot in the band’s lineup. Not long after, Barrett joined the band they changed their name to Pink Floyd (via Biography).
Barrett brought a lot to the table especially when it came to songwriting. “What was so stunning about Syd’s songs,” Waters told Rolling Stone, “was, through the whimsy and the crazy juxtaposition of ideas and words, there was a very powerful grasp of humanity. They were quintessentially human songs. And that is what I’ve always attempted to aspire to. In that sense, I feel a strong connection to him.”
However, Barretts increasingly erratic behavior was causing problems for the band, even during their concerts, According to Groovy History, Barret would sometimes change arrangements or lyrics without telling anyone, and would occasionally start a song in the wrong key on purpose. Barrett eventually suffered a mental breakdown, and the band knew they had to make a change, and brought in David Gilmour.