Changing the register tube of a clarinet significantly impacts its sound and playability. According to physicist Arthur H. Benade, an optimally designed register tube with a smaller diameter can minimize sharpness at the extremes of the scale caused by the register hole. This is because a smaller tube reduces unwanted turbulence and local disturbances within the bore.
Benade proposed an empirical formula relating the length and diameter of the register tube in his book “Fundamentals of Musical Acoustics.” This formula helps determine the optimal register tube dimensions for a specific clarinet. Utilizing a smaller register tube also necessitates a mechanism that automatically operates separate holes for the register function and throat Bb, improving the quality of the Bb note.
Another crucial aspect of register tube design is its placement. To avoid turbulence, the tube should protrude as little as possible into the bore. This means it should be positioned on the side or top of the bore, as seen in German clarinets or older Albert and Boehm system designs.
Using a smaller register tube also has implications for mouthpiece design. A clarinet with a small bore and smaller register tube might require a mouthpiece with a larger bore to compensate for altissimo flattening. Conversely, oversized register tubes in conventional clarinets often necessitate reducing the mouthpiece bore to bring high notes down to an acceptable pitch. The balance between register tube and mouthpiece dimensions is crucial for optimal tone and performance. Modifying a clarinet’s register tube requires expertise and should be performed by an experienced instrument repair technician.
