The waveform of a pure alternating current or voltage. It deviates about a zero point to a positive value and a negative value, consists of a single frequency and has a musical pitch, but a neutral timbre. Audio-range sine waves contain only the fundamental frequency, with no overtones and form the building-blocks for more complex sounds which are combinations of sine waves. Sub-audio sine waves are used by an LFO to modulate other waveforms to produce vibrato and tremolo. Also called a sinusoid. See Fourier analysis.