Final answer:
The trombone, which is part of the brass family and can slide from tone to tone, achieves pitch changes through a slide mechanism rather than valves or finger holes.
Step-by-step explanation:
The instrument in question, which belongs to the brass family, has a mouthpiece and bell but no valves, and is twice as long as a trumpet, is the trombone. The trombone is unique among brass instruments because it alters pitch through a slide mechanism rather than valves. Unlike players of instruments like the flute or oboe, who vary the length of the tube by opening and closing finger holes, trombone players change the length of the tube by moving a slide in and out. This sliding action allows for smooth transitions from tone to tone, known as glissando.
Therefore, a trombone can slide from each pitch to the next without the discrete steps created by valves or finger holes. Instruments such as the bugle, on the other hand, have a fixed length and can produce only a limited range of frequencies. In the context of wind instruments, the trombone showcases a unique method of sound production within the brass family, employing a slide to vary the air column length and alter pitches.