Overtone refers to a series of higher-frequency harmonics that are produced along with the fundamental frequency when a musical instrument produces a sound. These harmonics have frequencies that are integer multiples of the fundamental frequency. Overtone is an important characteristic of the timbre or tone quality of an instrument, which can affect the instrument's sound and tone color. It can also be used for music composition and performance techniques.
Overtone is usually produced through specific playing techniques and instrument design. For example, on string instruments like guitar, harp, and guzheng, overtones can be produced by pressing the strings at specific lengths and positions; while on woodwind instruments, overtones can be produced by adjusting the airflow and the shape and position of the mouth.