In 1991, Slocum played guitar in with Chris Taylor on a garage-band tape release called A Place to Hide Away (Part 1). He was a member of Love Coma, a Christian rock band, and in the early 1990s he met vocalist Leigh Bingham Nash while attending the same church in New Braunfels, TX. Slocum and Leigh formed Sixpence None the Richer; he and Nash are the band's only constant members. He co-wrote, with Nash, the song "Nervous In the Light of Dawn" for Nash's debut solo album Blue on Blue.
In 2006, Slocum toured with the band The Choir, playing bass. He has also played guitar with Over the Rhine, and currently, has played bass in the band the Astronaut Pushers.