Overtones
Any resonant frequency higher than the fundamental frequency in a musical sound.
Governing formula
First Overtone = 2nd Harmonic (for strings)
SI unit
Hz
In depth
In strings and open pipes, overtones are integer multiples of the fundamental. In non-linear systems like drums or bells, overtones can be non-integer multiples.
Examples in the real world
The rich, bright quality of a flute vs a clarinet caused by different overtone spectrum balances.