The bugle is one of the simplest brass instruments; it is essentially a small horn with no valves. All pitch control is done by varying the player's embouchure, since the bugle has no other mechanism for controlling pitch. Consequently, the bugle is limited to notes within the harmonic series. The bugle is used mainly in the military.
... generalizations) with a being non-zero. These solutions are also called the roots of the equation. The formula reads
<math>
x=\frac{-b \pm \sqrt ...