Final answer:
Overtones are the accompanying sound waves that are different multiples of the basic tone's frequency. They are higher resonant frequencies that are multiples of the fundamental frequency.
Step-by-step explanation:
The accompanying sound waves that are different multiples of the basic tone's frequency are called overtones. Overtones are higher resonant frequencies that are multiples of the fundamental frequency, also known as the first harmonic. The first overtone is actually the second harmonic.