Due to differences in shape, the baritone and euphonium horns can be distinguished, resulting in sound variations. The direction of the bell and the number of valves are also used to distinguish the two. These aren’t as conclusive.
The bore, or inside chamber of the instrument through which air passes when the player performs, is perhaps the most noticeable difference between the baritone and euphonium. The bore of the baritone is slightly smaller than that of the euphonium. Furthermore, the tubing in a baritone is mostly cylindrical, whereas the tubing in a euphonium is conical.
The size and shape of the bell are determined to some extent the shape of the bore on most air-powered instruments. As a result of the smaller tubing, baritone horns have slightly smaller bells than euphoniums. Overall, the baritone is a less bulky instrument to hold and play due to its smaller tubing and bell.
The tubing and bells of the baritone and euphonium horns are different, resulting in tonal color differences. These distinctions are easily discernible to the trained ear. Baritones have a brighter, lighter sound than euphoniums, making them ideal for cutting through a group. Euphoniums, on the other hand, have a mellower, warmer sound that is preferred players and composers for solos or when the ensemble needs to sound solid and deep. However, some baritones are built in such a way that they produce a color that is very similar to the technically larger euphonium, and vice versa.
To distinguish between the two instruments, people sometimes refer to the number of valves on a baritone and euphonium. Four valves are more common on a euphonium, while three are more common on a baritone. However, because some baritones are built with four valves, this is another characteristic that cannot be used definitively.
When marching bands in the twentieth century needed a valved tenor brass instrument, band directors and instrument makers created an instrument that was technically a hybrid of the baritone and euphonium due to its bore size. The bell on this instrument pointed forward, allowing the sound to easily reach the audience in the direction the performer marched. Despite the instrument’s hybrid nature, it was commonly referred to as a baritone. As a result, any baritone, euphonium, or hybrid of the two with a forward-facing bell is sometimes referred to as a baritone modern players and directors.
Another reason for the confusion between the baritone and the euphonium is that instrument manufacturers used to label student model instruments as baritones and upper level or professional model instruments as euphoniums. They did this despite the fact that the student model was a true euphonium all accounts. Some people mistakenly believe that the only difference between a baritone and a euphonium is the grade or quality.
Despite the fact that the baritone and euphonium have some distinct characteristics, the two instruments are extremely compatible. Both instruments can be used to replace a tenor brass voice in a group. They use the same fingerings and play in the same range and overtone series, so baritone players can usually play the euphonium and vice versa with minor adjustments. Due to the similarity in pitch and fingering, baritone players can perform pieces written for euphonium and euphonium players can perform pieces written for baritones. Many ensembles use a combination of instruments, while others are more selective and use only one or the other, depending on the sound the director desires.