Inharmonic describes a sound whose secondary frequencies (partials or overtones) are not integer multiples of the fundamental frequency.

In a harmonic sound (like that of a violin string or a flute), if the fundamental note is 100 Hz, its overtones will be found in exact multiples: 200 Hz, 300 Hz, 400 Hz, and so on. This simple mathematical relationship is what gives us the sensation of a clear and in-tune musical note.

In an inharmonic sound, this mathematical relationship does not exist.

Overtones appear at frequencies not entirely related to the fundamental (e.g., 157 Hz, 231 Hz, 412 Hz). Inharmonicity is characteristic of percussion instruments with metallic or membrane sounds, such as: Bells This complex structure of overtones is what gives these instruments their characteristic timbre and often a less defined or "untuneable" pitch compared to a piano or guitar.