Final answer:
The block on the Native American flute is known as a fipple, and it is crucial in creating the instrument's distinctive sound by directing airflow across the flute's air column.
Step-by-step explanation:
The block on a Native American flute is referred to as a fipple. The fipple functions similar to a whistle and is a key part of what gives the Native American flute its distinctive sound. This is because the fipple directs the air from the player’s breath across the flute's air column, causing it to vibrate and produce sound.
The fipple distinguishes the Native American flute from other flutes like the concert flute, which uses an embouchure hole over which the player blows directly. An important part of understanding how this and other woodwind instruments create music lies in the concept of open-pipe and closed-pipe resonators.
The fundamental frequency and the mix of overtones, which vary between instruments with closed pipes (like some Native American flutes) and open pipes (like most concert flutes), are what provide each instrument's unique sound. When a player covers or uncovers the finger holes of a flute, they are changing the length of the resonating air column, thus changing the frequency and the pitch of the note played.