Inharmonicity is when the overtones (frequency multiples) are not whole number multiples of the fundamental frequency. It sounds bad. Discordant, like playing

Inharmonicity is when the overtones (frequency multiples) are not whole number multiples of the fundamental frequency. It sounds bad. Discordant, like playing two notes directly next to each other on the keyboard. When designing a string or percussion instrument (or any resonator, in general, I suppose) one of the challenges is ensuring that you aren't creating undesired harmonics. With something like a piano with hundreds or thousands of strings that might be induced to resonate undesirably if even slightly out, or whose own movement might alter other parts and affect them, it becomes a significant challenge.