These "Counterparts" are printed separately as a "part book" to save space and page turns and to avoid any copyright issues. Most American trombone students and their teachers own the Voxman book. The primary intent is for recreational duet playing and for teaching studio. Duets are great fun, and help with key security, sight-reading, intonation, ensemble, style matching, confidence and independence. These duets will enhance the Voxman etudes with some interesting harmonies and other surprises.