Final answer:
Wind instruments like flutes and trombones alter pitch by changing the length of the air column within the instrument, using finger holes and slides respectively. The recorder is a type of end-blown flute that directs air through a mouthpiece.
Step-by-step explanation:
The student's question relates to musical instruments, particularly wind instruments like the flute. These instruments change pitch through the alteration of the length of their air column by covering or uncovering finger holes or by using mechanisms like slides or valves. For example, a flute's pitch is controlled by opening or closing the holes along the tube, which changes the effective length of the resonating air column within the instrument. Similarly, trombones use a sliding tube to achieve different pitches. In the case of a bugle, which has a fixed tube length, only a specific set of frequencies can be played. It is also important to note that while the recorder is an end-blown flute, it has a fipple or a block that directs air through a mouthpiece, differentiating it from flutes that rely on a player's air stream directed across an open hole at the top of the instrument.