One plus One consists of 14 solo pieces (Part I) with optional accompaniments (Part II). Each piece is based on a different scale or mode. The solo pieces can be played independently or with the accompaniment, which can be played on the same keyboard. Part I (solo) appears on either the right- or left-hand page, depending on how the players are to be seated at one keyboard. The accompaniments can be played by the teacher or by another student...