音乐上的偏差音（inharmonicity）是乐器的本性，代表乐器发出的泛音频率偏离其基本频率整数倍的特性。

钢琴调音（调律）中，所有平均律都需要微调，因为琴弦的刚性（stiffness）会产生偏差音。

1943年，Schuck和Young两位科学家首次测得钢琴的偏差音。相对于平均律的钢琴偏差音见Railsback曲线图。图中显示偏差音向钢琴左右两端扩大，偏离平均律的最大值约±30音分，差不多是一个半音的1/3。理论物理学家费曼在1961年的书信中描述金属线的刚性与琴弦频率偏移之间的关系如下式。真实的频率等于

In music, inharmonicity is the degree to which the frequencies of overtones (also known as partials or partial tones) depart from whole multiples of the fundamental frequency (harmonic series).

Acoustically, a note perceived to have a single distinct pitch in fact contains a variety of additional overtones. Many percussion instruments, such as cymbals, tam-tams, and chimes, create complex and inharmonic sounds.