填空题 Look at the four squares, , , , and , which indicate where the following sentence could be added to the passage. Where would the sentence best fit?
This is due to the beating of the double reed through which the air travels as it leaves the player's mouth.
The highest of the standard orchestral instruments, the flute is unlike the other woodwinds because it is held across the player's mouth. The air inside is set in vibration by the action of the airstream against the edge of the hole. The flute has no reed, so its tone is pure and creamy. In contrast, the oboe has a rasping, "sawtooth" configuration to its sound when played loud.