multitone

Multitone refers to a signal or sound that consists of two or more distinct sinusoidal components at different frequencies. In the time domain it is the sum of several sine waves, and in the frequency domain its spectrum contains multiple discrete lines corresponding to the constituent tones. The relative amplitudes and phases of these components determine the overall timbre, loudness, and waveform shape. If the tones share a common period, the multitone is periodic and can be described by a fundamental frequency equal to the greatest common divisor of the component frequencies; otherwise the signal is aperiodic.

Multitone signals are widely used in testing, calibration, and analysis of audio and electronic systems. Additive synthesis and controlled multisines are employed to probe linearity, impulse response, distortion, and dynamic range. In telecommunications and digital communications, the idea of using many simultaneous carriers is central to multitone or multicarrier modulation schemes; orthogonal frequency-division multiplexing (OFDM) is a well-known example, used in DSL, cable modems, Wi-Fi, and 4G/5G networks.

In music and acoustics, simultaneous tones create chords and polyphonic textures; while the term multitone is not a standard label in traditional music theory, it captures the concept of several tones sounding together. The concept also appears in signal processing literature in contexts such as multitone testing and multitone synthesis.