Captain Beyond is unique among guitar-driven hard rock albums in that it contains a wide range of influences, including Latin and jazz, often with various time signatures and a broad range of dynamics within the same song. Most of the album consists of three medleys of tightly arranged interconnected songs. The first starts with "Dancing Madly Backwards (on a Sea of Air)" and ends with "Myopic Void". The second starts with "Thousand Days of Yesterdays (Intro)" and ends with "Thousand Days of Yesterdays (Time Since Come and Gone)". The third starts with "I Can't Feel Nothin' (Part 1)" and finishes the album. Songs flow directly into each other without any lag time between selections, a feature that is shared with other more progressive bands of the era such as The Moody Blues and Jethro Tull.
All of the songwriting was credited to lead vocalist Rod Evans and drummer Bobby Caldwell. However, the songs were in fact written by the group as a whole. Due to their still binding contracts with Iron Butterfly, guitarist Larry Reinhardt and bassist Lee Dorman could not be listed as songwriters on this record for legal reasons.