Complex sentence: Volk and Smith left the band after the Sullivan performance and Levin re-teamed with them in Brotherhood, a promising band signed to RCA that never got its full chance to be heard, owing to the members' lingering contractual obligations to Columbia Records from their Raiders work.
Split into simpler sentences: Volk and Smith left the band after the Sullivan performance and Levin re-teamed with them in Brotherhood. The band was signed to RCA, but were hindered by the members' lingering contractual obligations to Columbia Records from their Raiders work.