A spectrum analyzer is a device used to examine the composition of some electrical, acoustic, or optical waveform. An analogue spectrum analyzer uses either a variable band pass filter whose mid-frequency is automatically tuned (shifted, swept) through the range of frequencies of which the composition is to be measured or a super heterodyne receiver where the local oscillator is swept through a range of frequencies. A digital spectrum analyzer uses the Fast Fourier Transform (FFT), a mathematical process that transforms a waveform into the components of its frequency. As a result, computer programs can compute such transforms, and makes audio processing easier.