Abstract: This invention relates to real time control either in compression or expansion of the amplitude of electrical waves and more specifically to a real time expandor or compressor of the amplitude of sound waves. In general a source of waves which may be the electrical equivalent of a sound including continuous discourse is applied to a plurality of first filters whose output is connected to respective power circuits, that is, circuits that produce at its output a wave whose amplitude is a power, either greater or less than one, of the amplitude of the wave applied to its input. The outputs of the power circuits are applied to respective second filters which are similar to the filters connected to the input of the power circuits and the output of the second filters is connected to a utilization device. Amplifiers may be connected where needed.