In a large bore symphony tenor trombone having a detachable and interchangeable bass mouthpipe, the improvement comprising, interchanging the bass mouthpipe with a tenor mouthpipe that will accommodate a tenor shank mouthpiece at its proximate end and that tapers from its proximate end to its distal end to the straight bore dimension of the large bore symphony tenor trombone, whereby an acoustically shaped air column is created between a tenor shank mouthpiece and the straight bore dimension of the large bore symphony tenor trombone, and whereby the tenor mouthpipe changes the acoustical and playing characteristics of the large bore symphony tenor trombone to those of a small bore tenor trombone.