S-K MECHANISM
The S-K mechanism is so designed that there are two separate holes for the middle line Bb and the twelfths. This creates a clear Bb, and better intonation for the twelfths. The mechanism requires no new fingering methods, and no special maintenance. It uses the exact size necessary for the little vent hole, and provides a resonance hole which opens automatically when the vent hole is used for the Bb third line, thus producing a clear and resonant Bb. The resonance hole closes automatically when the thumb ring is pushed, and leaves only the properly sized little vent hole opened by the speaker or vent key when the upper register is played. The S-K mechanism is not a gimmick, but rather an acoustical correction to the fundamental design of the clarinet.
Frank Kaspar the elder, carried on his mouthpiece business in Ann Arbor, Michigan. His cousin, likewise create excellent mouthpieces in Cicero, Ill., a suburb of Chicago. My connection with Frank Kaspar in Ann Arbor existed only through telephone calls at which time I would place an order for mouthpieces. All of my students played the Ann Arbor, and it was Frank who made me my first very fine mouthpiece.
William Stubbins was Professor of Clarinet at the University of Michigan, whose treatises on acoustics have been widely acclaimed.