Definition of euphonium in English English dictionary
A valved brass instrument, a sax horn, the tenor of the tuba family of instruments, having the appearance very similar to that of a tuba. It is similar to and often used instead of a "Baritone" horn. (A true Baritone has a cylindrical tubing, while the Euphonium tubing is conical, though they both cover the same range of tones. This relationship is also between the Trumpet and Cornet respectively.)
A valved brass instrument, a sax horn, the tenor of the tuba family of instruments, having the appearance very similar to that of a tuba. It is similar to and often used instead of a "Baritone" horn. (A true Baritone has a cylindrical tubing, while the Euphonium tubing is conical, though they both cover the same range of tones. This relationship is also between the Trumpet [cylindrical] and Cornet [conical] respectively.)"
or tenor tuba Large valved brass instrument, the leading lower-pitched instrument in military bands. It developed from the valved bugle and cornet in Germany 1840. It has four valves and a wide conical bore resembling the tuba's. Its range is an octave below the trumpet and cornet. It is played either vertically or with the bell facing forward. The very similar baritone has the same range and transposition and is distinguished only by its narrower bore. Both are essential members of bands of all kinds and are often given significant solo roles
It is similar to the Tuba, pitched in B flat and has a range of about three octaves and produces a velvety tone