Everyone knows what a trombone looks like. Even modern valve trombones maintain the familiar shape of the slide trombone. In the nineteenth-century, however, when instrument designers competed with each others’ various valve configurations, there seemed no reason to keep their creations looking like a slide trombone. The shape of the bore, not the shape into which the tubing is bent, determines what will sound like a trombone. Adolphe Sax introduced many odd-looking valve trombones, none odder than his six independent valve invention.
The very earliest valves did not work especially well, and it took a while to find the optimum valve lengths and combinations. By the middle of the century, though, two basic configurations became standard. Most valved instruments came with at least three of either piston or rotary valves. Most often, the first valve lowered the sounding length by one whole step, the second by one half step, and the third by one and one half steps.
A brass tube must be lengthened by about 6% to lower the pitch by one half step. If the second valve is exactly enough to accomplish that when it is the only one engaged, it will clearly not be enough in combinations with other valves. The longer the basic length, the more tubing must be added to get valve combinations in tune. That is why modern tubas always have at least four valves. Nineteenth-century makers experimented with all kinds of ways to get valve combinations in tune, including using more than four valves.
Sax decided to approach the problem another way. He made a valved trombone with six valves that would not be used in combination. With no valves in use, his trombone was equivalent in length to a slide trombone in seventh position, or with the slide extended out as far as it will go. Each valve actually shortened this tube by enough to provide the equivalent of each other slide position, finishing with the equivalent of first position, or with the slide as far in as it will go. In theory, it would play perfectly in tune. He tried out several different configurations of this basic idea.
Actually, it doesn’t play perfectly in tune, but nothing in the education of trombonists provided sufficient attention to ensemble playing that anyone realized that yet. The design had a couple of more immediate problems. It makes an extremely heavy instrument. Worse, it required valves with a double channel with eight holes. That is, the entire air column passed through each valve twice. It is extremely difficult to keep that complicated a valve air tight. A valve that leaks air is no good.
When Sax tried to simplify the valves, he could no longer attach them all to the same bell. Therefore, his second model required not only six valves, but seven different bells. As with the first model, it came in different shapes. Somewhere, and years ago, I have seen a model where the seven bells surrounded the player’s head like a halo. It seems to me that it was built and marketed by Sax’s one time partner and later rival, Henry Distin. I couldn’t find it online. Not even Will Kimball has that one!