Abstract: A brass instrument mouthpiece is described as incorporating an adjustable cup depth to enhance performance in the upper register of the instrument, without sacrificing tonal quality in the lower register. In accordance with a preferred embodiment of the invention, an interchangeable mouthpiece rim and sleeve are correspondingly threaded to flushingly fit together, and to receive a threaded mouthpiece shank and cup to an adjustable depth. A threaded lock is secured to the shank when the cup is located at the depth desired with respect to the rim, to then set the mouthpiece ready for use.