Ondertonen

Ondertonen, in acoustics and music theory, refers to subharmonics—the frequencies that would lie below the fundamental frequency if a vibrating system produced divisions of that fundamental. For a given fundamental f, undertones have frequencies such as f/2, f/3, f/4, and so on. In theory they form a series opposite to the familiar overtone (harmonic) series, which presents multiples of the fundamental. In practice, undertones are not as consistently present as overtones; their existence and strength depend on nonlinear behavior in the vibrating instrument or voice, or on electronic processing that deliberately generates subharmonics.

Historically, undertones have been discussed as a conceptual counterpart to overtones within the study of harmony, psychoacoustics, and the physics of musical tones. While the overtone series underpins standard tuning and timbre in Western music, undertones have largely remained outside mainstream practice. They have appeared in certain speculative or experimental contexts, especially in microtonal and subharmonic tuning projects during the 20th century.

In performance and synthesis, undertones can be encountered or produced in several ways. Some voice techniques and wind or string instrument phenomena can generate subharmonics, though they are usually weaker than the main pitch. In electronic music and sound design, subharmonic oscillators and processing can deliberately create f/2, f/3, f/4, etc., to explore tunings and textures beyond the overtone series. Undertones are therefore mainly discussed in specialized or theoretical contexts rather than as a standard feature of ordinary musical practice.

See also: overtone series, subharmonics, harmonic series, microtonality, just intonation.