The solo instrument within the lower brass family. Euphoniums are available with either 3 or 4 valves and with or without compensation. The compensation system was invented by David Blaikley at Boosey & Co. in 1874 and is still the industry standard for improved tuning on large brass instruments.
The system works by automatically bringing into play additional lengths of tubing when the lowest valve is used in combination with any of the other valves. This compensates for the inherent sharpness of pitch in the lower register of large piston-valved instruments.