Noise: White sound or 'noise' consists of all audible frequencies sounding randomly (i.e each tone is independent of another before or after). No frequency remains at a steady dynamic level, so that white sound seems to have a rapid internal motion within the overall sound. If noise is filtered by a band pass filter the output will be noise with an apparent pitch given by the centre frequency of the band. If this is voltage- controlled then the apparent pitch of the noise can be controlled by the keyboard. 'Pink noise' is white noise filtered through a low-pass filter, and the difference has to do with power distribution. With white noise, you get equal power per unit bandwidth, eg the power from, say, 1-2KHz will be the same as in (say) 5-6KHz or 16-17 KHz. With pink noise, you get equal power per octave, eg the power from 1-2 KHz will be the same as the power in 4-8 KHz or 10-20 KHz. You therefore have more control over its effect (particularly when keyboard controlled) You can get pink noise by passing white noise through a 3 dB/octave filter. Tones have the same energies within similar ranges.