- low E should be dead on with 64
- low E flat should be dead on with 54
- low D should be just about dead on with 564 (234 is usually flat)
- low C should be dead on with 5634
Yes, there are in tune combinations for low D-flat and low B-natural as well, but I don't encounter those pitches and written music very often, myself.
The negative is that the left hand is occupied with those valves, and the only way to operate the 1st slide for micro tuning is with a right hand thumb trigger. Most likely, first valve C would need the 1st slide all the way in, whereas most of the other pitches which involve 1st valve would probably be triggered out an inch or more, so that's a lot of constant holding the 1st slide out in it's most common position against the trigger's spring tension.
Being a vintage B&S 4/4, I would expect the open D and 2nd valve D-flat to both be flat.
This instrument is for sale on Facebook marketplace. I think it's in Pennsylvania. The point of the post wasn't to alert people that it's for sale, but to discuss this valve system.
Basically, the 5th and 6th valves function as FF subcontrabass tuba 1st and 2nd valves.
The mouth pipe receiver appears to me to be positioned quite low, but whatever on that; that isn't the point of the post... Based on most threads though, I expect it to become the main topic.
