Complex sentence: After joining Dream Theater when it was still known as Majesty, Collins recorded six tracks with the band that became the famous "Majesty Demos" that were mostly circulated by the band in the form of tapes given out at shows.
Split into simpler sentences: After joining Dream Theater still known at the time as Majesty, Collins recorded six tracks with the band. These recordings became the famous "Majesty Demos" that were mostly circulated by the band in the form of tapes given out at shows.