Complex sentence: As Baldry's music drifted more towards the cabaret market, Dwight became disenchanted with the band, and so simultaneously began to develop songwriting skills in collaboration with Bernie Taupin whilst working as a session musician.
Split into simpler sentences: As Baldry's music drifted more towards the cabaret market, Dwight became disenchanted with the band. He began to develop his songwriting skills in collaboration with Bernie Taupin, and worked as a session musician.