Cornet-A-Pistons, a musical wind instrument of metal, the mechanism of which enables it to give all the intervals of the chromatic scale as far as the low F sharp. It has a compass of about two octaves and two notes, though the extreme low and high notes of its scale are of hazardous utterance. There are cornets in C, B fiat, A, A flat, G, F, E natural, E flat, and D. Those in A flat, A natural, and B flat are the best and the most correct in intonation, having fewer doubtful or bad notes than the others. That in C, the highest of all, is somewhat difficult to play. As to the relative pitch of this instrument with that of other brass instruments of its kind, the first low sound of the cornet in C is an octave above that of the trumpet in C, and two octaves above that of the horn in the same key. The cornet-a-pistons is not an instrument of much dignity of tone, in this respect falling below the trumpet; neither has it the nobility of the horn. "When heard however in the orchestra, in combination with other instruments of its class, especially with the trombones, whose sonority reenforces its tone and takes away its trivial character, it produces excellent effects.

It is useful also in rendering rapid diatonic or chromatic passages which are impracticable for either the trombones or horns. - A wind instrument named the cornet was formerly in use, but has given place to the hautboy. It consisted of a curved tube of brass, about three feet long, increasing in diameter from the mouthpiece to the lower end.