The euphonium is a deep brass instrument. Its sound is reminiscent of the tuba, with the difference that it does not target the bass, but the tenor and baritone areas, which is why it is often referred to as the tenor tuba in English-speaking countries. The basic tuning of the euphonium is in B flat; it sounds an octave lower than a trumpet and an octave higher than a tuba in this tuning. Euphonium, baritone and tenor horn are three instruments from the same family with the same keynote and tuning; however, they differ in sound and function. The difference lies in the shape of the instrument: the euphonium is already conical from the mouthpiece; The baritone and tenor horn, on the other hand, have a cylindrical bore that only changes into a conical shape in the second half of the sound tube, behind the valves. The tenor horn also has a significantly narrower length, which is why it sounds lighter and the higher notes are easier to blow. The euphonium has a full, darker sound. The sound of the baritone lies between the tenor horn and the euphonium. Due to the conical shape of the euphonium, it is physically larger and heavier than the baritone and tenor horn and requires more air to be blown.