The euphonium is a tenor brass instrument in the same family as the trumpet, trombone, and tuba. It possesses a low, mellow sound and is often used in brass bands and concert bands. The standard euphonium has a range of three octaves and a whole tone, from B♭1 to C4, although some euphoniums can play higher or lower notes.
Here is the range of a standard euphonium in treble clef:
```
B♭1 C2 D2 E♭2 F2 G2 A2 B♭2
C3 D3 E♭3 F3 G3 A3 B♭3 C4
```
The euphonium is also capable of playing notes in the pedal range, which are below the standard range. These notes are typically written in bass clef.
The euphonium is a versatile instrument that can be used to play a variety of music, from classical to jazz to pop. It is a popular choice for soloists and ensemble players alike.