In other words, overtones are all pitches higher than the lowest pitch within an individual sound; the fundamental is the lowest pitch. ... The relative volume or amplitude of various overtone partials is one of the key identifying features of timbre, or the individual characteristic of a sound.
If the overtone is harmonic, the pitch does not change. ... A sound without a distinct pitch is usually regarded as unpleasant. So, an instrument with harmonic overtones means that you can add the harmonics in various amounts to adjust the tone quality while preserving a sense of pitch and producing a pleasing sound.