Complex sentence: This was the beginning of the transition to the band that we are now, in that the circumstances forced us to stay as a three piece, handle the vocals ourselves and go back to the band's roots in a more blues/rock format.
Split into simpler sentences: This was the beginning of the transition to the band that they are now. Circumstances forced them to stay as a three-piece, handle the vocals themselves and go back to the band's roots in a more blues/rock format.