In an age of microchips, why are books becoming bigger? Timely arrivals for Christmas - such as the Gramophone's 1998 Good Classical CD Guide (pounds 15.99) and the Penguin Compact Discs Yearbook 1997/8 (pounds 13.99) - are full of massy substance and will require of Santa an outsize stocking. Granted, the kind of person who receives the Gramophone guide will doubtless have plenty of shelf space. A fine connoisseurship is implicit in both this publication and its slimmer, more concise Penguin rival. It's nice to know that people are sufficiently wealthy to choose among full-price CDs, oiling the wheels of the ailing record industry. Written by experts, both books are faultless in the scope of their authority. But for sheer inclusiveness, and pounds 2 more, the Gramophone, with clearer layout, appears the better offer.

Content, of course, dictates the size of reference books, a clear case in which the CD-Rom has the edge on the ancient folio. Size, in the case of the Rough Guide to Opera (Penguin, pounds 16.99), is more a matter of making things easy. It has plenty of pictures and a minimalist look that belongs to our time. All books of this kind are footnotes to Kobbe, the classic book of opera plots. Even so, each rethink refreshes the spirit for its generation, and this guide, like companions on World Music, Jazz and Classical, is no exception. There are lively anecdotes on subjects as varied as Verdi in rehearsal or Mussorgsky and vodka. Top recordings are copiously recommended. A useful guide for opera lovers, this book should also prove helpful to students.

Rather than suggest recordings, a Schubert biography and a second volume of Mozart letters packaged by Everyman and EMI (both pounds 25 each) include them with the book; three discs each. Schnabel, Fischer-Dieskau and Richter are just some of the Schubert performers, drawn from EMI's vast archive. And why not? Their work is part of the composer's performance history. These elegant publications belong to the tradition of music appreciation, for which no theoretical knowledge of music is needed. Instead, context unlocks creativity, through letters and - in Schubert's case - through the detailed iconography of Biedermeier Vienna. The inclusion of discs is no gimmick from the pop-up school of publishing. It is a genuine adjunct, aiding a subject beset by the paradox of its own resistance to explanation.

Before the days of mass recordings, when highbrow and lowbrow were words of real validity, music appreciation was sternly taught as a branch of self-improvement. All that was changed by recording, which also changed music history itself, whether jazz, pop or classical. Though the late Sir Georg Solti's memoirs Solti on Solti (Chatto & Windus, pounds 20) are best taken in small doses, they show how his reclame was founded on vinyl as much as the concert hall. In a somewhat humourless tone, he gives accounts of Strauss, Bartk and Kodly, but little insight into why he was an object of love. Perhaps the memoir form betrays him.

Edited by Robert Gottlieb, Bloomsbury's Reading Jazz (pounds 20) is a monster anthology, a thesaurus of autobiography, reportage and criticism to gladden the hearts of jazz lovers and lovers of hyperbole alike. Amid so many "great geniuses" and "brilliant performers", it's surprising there's any room left for mere ordinary musicians. Still, that's all part of the fun, writers on jazz having no brief to be objective. You don't even need to know much about the subject to enjoy these portraits of Bechet, Armstrong, Ellington, Carmichael, Davis, Mingus and many others.

Jazz and the history of sound recording grew up side by side in our century, as did recording and music for the movies. Russell Lack in Twenty-Four Frames Under (Quartet, pounds 15) provides a comprehensive account of the use of music in cinema, from Saint-Saens's first experiments . Lack gives chapters on copyright, scoring, politics, the French New Wave, jazz and Surrealism. His main thrust, however, is the aesthetics of film music, discussed with informed authority.

Allan Moore's analytical Cambridge Music Handbook on Sgt Pepper's Lonely Hearts Club Band (pounds 7.95) begs the question as to whether this admittedly special concept album is yet ready for inclusion in the Western canon. Recording made pop happen, and this study is merely the other side of the coin from the possible dumbing-down of appreciation through technology. Round his voice-leading graphs (not much use to your average Beatles' fan) the author weaves a pleasing narrative, without a trace of irony. His book will be hung in the groves of Academe, and widely read at Swift's Academy of Lagado.