Brass Instrument Valves: How They Work
Have you ever wondered how the valves on brass instruments work? As a music educator, in case of instrument damage it is important to know how instruments work. This document will cover how valves on brass instruments work and focus on the difference in design. There are two different types of valves found on brass instruments: the piston valve and the rotary valve. The piston valve is mainly found on the trumpet, valve trombone, euphonium, and some tuba. The rotary valve is mainly found on the French horn, advanced tubas, and some rotary trumpets. Valves are used to change the length of tube being used on the instrument, causing the pitch being produced to change.
Brass instruments use valves because they are quick, easy to use mechanisms that allow the musician’s are stream to change paths with little to no interruption. There is little space in between the valve and its casing. The width of space can be measured even slimmer than a strand of hair. To keep the valves in top usable condition, they must be lubricated and cleaned on a regular basis.
Both of these systems are useful, especially when it comes to the instrument design. The reason that there are two different types of valves is to made the instrument (based off of its design) more comfortable to play.
Piston Valves:
As seen in the pictures above, in this particular design of the piston valves, the actual valve sits on top of a spring. When the valve is pressed down, the spring shrinks. This allows the passage that air travels through to change direction and access different areas of tubing on the instrument. When the pressure applied by the musician’s finger is released, the spring expands forcing the valve to lift as seen in the middle picture.
How does the tubing on the instrument match up with the passages on the valves?
To get the tubing on the instrument to match up with the passages on the valves, there is a little part called a valve guide (shown above) that has little ends that meet and lock into divots formed on the valve casing. The valve guide is also locked into place horizontally on the piston valve so that the valve can not rotate side to side. Some variations of the piston valve will have the spring pushing up on the valve guide inside or outside the upper part of the valve instead of pushing on the bottom of the valve (Right side picture on page 1).
Rotary Valves:
The Rotary valve is very different from the piston valve. Instead of moving vertically like the piston valve, the rotary valve rotates horizontally. With an attached valve guide on the bottom (shown in the bottom left picture), the valve can only rotate so far allowing the tubing of the instrument to match up with the valve passages. To create the valves rotation, the musician presses down on a trigger that moves a small metal rod attached to a string that is also looped around and attached by a screw to the valve guide on the bottom of the valve (see both top left and right side pictures). When the metal rod moves it pulls that string which then pulls on the guide causing the valve to rotate. To move back, the same trigger that is pressed by the musician is attached to a spring that twists further into itself when pressed and then expands back when released, bringing the rod, the string, and the guide back to their original positions. This is also a quick action process so that the musician’s air flow is hardly interrupted by the movement of the valve.
As shown, valves are very effective to not only the playability of the instrument, but also the design of the instrument. Valves are easy to use and don’t cause extra problems for the musician (unless they are not treated properly). This makes valves ideal instead of using keys like those found on a clarinet and saxophone. Piston and rotary valves are simply easy to use, reliable, and effective.