AM stereo is any of a number of mutually-incompatible techniques for broadcasting two-channel audio in the mediumwave band in a manner that is compatible with receivers designed for standard amplitude modulation. There are two main classes of systems: independent sideband (ISB) systems, promoted principally by American broadcast engineer Leonard Kahn; and quadrature amplitude modulation (QAM) multiplexing systems (conceptually closer to FM stereo), of which the best known is Motorola's C-QUAM.
A famous European transmitter using AM stereo is Villebon sur Yvette on 864 kHz, which tranmits Radio Bleue.
