Sims, a native of Tulsa, OK, formed the Tulsa County Band with drummer Jamie Oldaker and bassist Carl Radle. Together, they helped develop the country-rock hybrid that became known as the "Tulsa sound." Introduced to Clapton through Radle, the threesome first backed the guitarist on his 1974 album 461 Ocean Boulevard. Though it was a collaborative effort, Sims told Tulsa People in 2010, "they weren't going to name it 'Eric Clapton and Tulsa County,' because Eric was already a solo act." The band stayed on as Clapton's backers for nine years, recording on several albums, including the classic Slowhand.
Sims, who played on Bob Seger's album Back in '72 with Oldaker, went on to play his customized Hammond B-3 organ with many other acts, including J.J. Cale, Peter Tosh and Vince Gill. After a 10-year hiatus from music, he released his only solo album, Within Arm's Reach, in 2008. Clapton dedicated his December 10th show in Tokyo to his late friend.