The air itself is the vibrator in the primary sense. The standing waves are significantly confined within the instrument itself. The air-stream passes through the player's vibrating lips, so gaining intermittent access to the short air column which is to be made to vibrate. The tubular body has a bore profile that is predominantly cylindrical. The body can be lengthened or shortened by connecting or disconnecting auxiliary lengths of tube. With lengths of tube (crooks etc.) to set nominal pitches preparatory to playing.
Valve trumpets with short air column (less than 2 m) and with crooks
Hornbostel - Sachs
Valve trumpets with short air column (less than 2 m)