From the beginning of commercial recording, new discs purported to be indistinguishable from The Real Thing have regularly been put in circulation. Seen in perspective, many of these releases have a genuine claim to be milestones. Although lacking absolute verisimilitude, they supply the ear and the imagination with all necessary materials for re-creation of the original. On the basis of what they give us we can know how the young Caruso sang, appreciate the distinctive qualities of Parsifal under Karl Muck's baton, or sense the type of ensemble Toscanini created in his years with the New York Philharmonic.

Since the concept of high fidelity became important some dozen years ago, the claims of technical improvements have multiplied tenfold. In many cases the revolutionary production has offered no more than sensational effects: the first hearing was fascinating and the second disillusioning as the gap between sound and substance became clearer. Other innovations with better claims to musical interest survived rehearing to acquire in time the status of classics. If we return to them today, we have no difficulty spotting their weaknesses but we find them still pleasing.

Records sound like records because they provide a different sort of experience than live music. This difference is made up of many factors. Some of them are obvious, such as the fact that we associate recorded and live music with our responses and behavior in different types of environments and social settings. (Music often sounds best to me when I can dress informally and sit in something more comfortable than a theatre seat.) From the technical standpoint, records differ from live music to the degree that they fail to convey the true color, texture, complexity, range, intensity, pulse, and pitch of the original. Any alteration of one of these factors is distortion, although we generally use that word only for effects so pronounced that they can be stated quantitatively on the basis of standard tests. Yet it is the accumulation of distortion, the fitting together of fractional bits until the total reaches the threshold of our awareness, that makes records sound like records. The sound may be good; but if you know The Real Thing, you know that what you are hearing is only a clever imitation.