Why a dependent fifth valve?
No different than many bass trombones, the dependent valve was controversial from its inception. Now a German company offers a dependent rotor valve F tuba used by a famous German brass quintet. I’m flattered. Some of the greatest players in tuba history played four valve tubas. There is an undeniable more open feel to the tuba without the addition of a fifth valve in the open horn. On the other hand there are some distinct advantages to having a fifth valve in the low register. The dependent fifth valve joins the advantages of both. The argument against the dependent fifth valve is the loss of an alternate fingering for the half step or whole step above the open second partial. There are other ways to deal with that one note. In fact many great tuba players have done so with four valve tubas. If the player agrees that the overall quality of the instrument is preferable without the fifth valve in the open bugle, the question is simply whether an alternate fingering for one note (two with compromise) outweighs the advantage of feel and sound on 47 other notes. Putting the valve in the large side of the main tuning slide as on the Chicago SymphonyYork means .812” rotor on CC and BBb tubas. The F tuba would require a whopping .866” rotor. Big, sluggish and a significant interruption to the open horn. Putting it in the small side of the main tuning slide means taking 2” out of the tuning slide and still putting an interruption in the open bugle. Putting it ahead of the main cluster, in the lead pipe, is the most interruptive of all and requires the smallest tubing of any choice. Putting it in the fourth tubing allows it to be the larger .750” bore for a great low register and keeps it out of the way of the open bugle when not in use. By positioning the fifth rotor in the fourth tubing it was possible to design the operating lever without rods and levers. The action is direct and positive.