Conversation so far:
what did casey do in early career?
he spent time in Detroit as a disc jockey for radio station WJBK-AM (and doing such shows as The Lone Ranger and Sergeant Preston of the Yukon).
how long did he stay there?
CANNOTANSWER.
what did he do next?
before moving to California.
At KYA in San Francisco, the general manager first suggested he tone down his 'platter patter' and talk about the records instead.
did he follow his advice?
Kasem demurred at first, because it was not what was normally expected in the industry.
what did he do instead?
He created a show which mixed in biographical tidbits about the artists' records he played, and attracted the attention of Bill Gavin who tried to recruit him as a partner.
did they end up becoming partners?
After Kasem joined KRLA in Los Angeles in 1963, his career really started to blossom and he championed the R&B music of East L.A.

Question: what did he do as it blossomed?
Self-contained rewrite: what did Casey Kasem do as his musical career started to blossom in KRLA in Los Angeles?