Two distinct varieties of audio cassette recorders have developed since cassettes were first introduced in the mid-Sixties. One follows the original reasoning behind the cassette as a small, compact medium for recording and playing back audio information. The other is a spin-off from this, the use of the cassette as a very high fidelity device capable of delivering exceptional sound quality in a very small format. The latter has been made possible through the invention and application of noise reduction systems such as the Dolby circuitry and the sophistication of the internal mechanism of the cassette player to achieve excellent tape stability. But the price of these ‘cassette decks’ (they contain no speakers and are meant to be used with a stereo system) is over two hundred dollars with noise reduction and they are an event unto themselves which we’ll take up in another column.