Final answer:
A repeating complex tone or pure tone is called a musical note, which is the basic unit of music with specific names. Each musical note's unique sound, or timbre, is shaped by the fundamental frequency and its overtones, leading to distinctive qualities in musical instruments and voices.
Step-by-step explanation:
When a complex tone or pure tone repeats, it is known as a musical note. The basic unit of music with specific names like A, B, C, and so on is combined to generate tunes. Every musical note has a fundamental frequency, which is the primary frequency, and may also include additional frequencies called overtones. The number and relative intensity of these frequencies define the unique sound of an instrument or voice.
For instance, middle C on a trumpet sounds different from middle C on a clarinet, due to the differences in overtones and their intensities. This distinct combination contributes to the timbre of the sound, a quality that influences the tone's purity and is defined by the interplay of frequency, amplitude, and timing of sound waves.