Goudenhooft's "Apercu du Trombone Basse Double Noix, volume 1" (published French title) is a collection of 42 etudes designed to familiarize the player with the double valve bass trombone. Though the book was written at a time when all basses used dependant valves, this book is appropriate for independent valved instruments as well. Many are in duet form, with the idea that a tenor trombonist would play the upper line to compliment the bass line. The two parts are not identical, but are instead often in counterpoint (the tenor trombone part is not required unless you wish to perform the etudes as duets). -cdp