Complex sentence: During the session, he decided that they should discard the rough version of "Third Stone from the Sun" from December 13 and re-record the song; they completed a basic track for the piece, but were unable to achieve a finished master.
Split into simpler sentences: During the session, he decided that they should discard the rough version of "Third Stone from the Sun" that they had recorded on December 13 and re-record the song. They completed a basic track for the piece, but were unable to achieve a finished master.