Description The keyed trumpet is a brass instrument that makes use of keyed openings in its bore rather than extensions of the length of the bore as the means of playing all the notes of the chromatic scale. The instrument's popularity reached its high-point around the turn of the nineteenth century; but it waned with the emergence of the valved trumpet in the early nineteenth century and it is rarely seen in modern performances.
On Wikipedia https://en.wikipedia.org/wiki/Keyed_trumpet
Parent instrument Trumpet