Final answer:
A bugle is a brass instrument with a fixed tube length that produces a limited range of frequencies, playing notes in the harmonic series of its key.
Step-by-step explanation:
A bugle is a bell front brass instrument which is known for having a fixed length, meaning it can only produce a limited range of frequencies. Unlike wind instruments like the flute, oboe, or trombone, which can change the length of their resonating tube to produce a wider range of notes, the bugle has no finger holes or sliding parts to alter the pitch. Therefore, the bugle plays notes in the harmonic series of its fundamental tone.