Complex sentence: Jarrett had been a member of Miles Davis'band, which recorded for Columbia, until shortly before making "Expectations"; the label subsequently signed him to his own contract, but subsequently broke the contract by dropping Jarrett after the record's release.
Split into simpler sentences: Jarrett had been a member of Miles Davis'band, which recorded for Columbia, until shortly before making Expectations. The record label subsequently signed him to a contract but then broke the contract by dropping Jarrett after the record's release.