Sims died soon after, and Bernie Young took over as bandleader; Simpson remained in the ensemble until 1930.
He recorded as a leader under various names, with Jabbo Smith and Milt Hinton as sidemen.
In 1933 he cut a few sides with Half Pint Jaxon, a female impersonator.
Soon after his recordings with Jaxon, Simpson apparently became mentally disturbed, and was institutionalized in 1935 in Elgin, Illinois.
He recorded solo piano numbers on the grounds of the hospital in the middle of the 1940s.