A technique, usually performed using a DSP algorithm, that allows complex, dynamically changing audio waveforms to be described mathematically as sums of sine waves at various frequencies, amplitudes, and phases. The Fourier transform allows a function that represents an audio signal (signals are in the time domain because they exist in time) to be transformed to another function which represents the same signal in the frequency domain. The signal in the frequency domain is called a spectrum, and the same signal in the time domain is called a waveform.