BOOK REVIEW / Donkeys and billiards: Jonathan Keates tackles a tempting feast of operatic work. 'The Viking Opera Guide' - Ed. Amanda Holden, Nicholas Kenyon and Stephen Walsh: Viking, 60 pounds

One of my favourite silly games is imagining the operas that might have been created by the great masters from the fictional and dramatic successes of their respective eras. How about Rossini's Pride and Prejudice, for example, full of impossibly roulade-encrusted arias for 'Elisabetta' and 'Darci'? Why didn't Mozart turn The School For Scandal into La Scuola delle Pettegolezze, with Sir Peter Teazle singing 'Contessa, perdono]' to his wronged wife in the last act? Little Dorrit would have given Verdi a splendid opportunity for one of his great father-daughter duets. As for that unwritten meisterwerk, Wagner's Middlemarch, with Casaubon as a sort of Beckmesser, Bulstrode doing a Victorian Alberich and Dorothea yodelling to Ladislaw over a Bayreuth-sized band, I leave this to your consideration.

Among the countless pleasures of the Viking Opera Guide is discovering that opera is essentially a huge theatrical sausage factory, in which everything can somehow be rendered down for musico-dramatic consumption. This omnivorous resilience effectively knocks out the standard objection to ludicrous plots, since, as Il Trovatore, a habitual but undeserving butt of such criticism, reveals, a feast of good tunes well sung makes anything convincing. Thus the act of faith we commit every time we enter an opera house validates Lortzing's Der Wildschutz, featuring a dead donkey and a game of billiards, Spontini's Nurmahal, requiring the services of a performing elephant, and Auber's La muette de Portici, whose dumb heroine Fenella jumps into the crater of Vesuvius.

The traditional attitude to these three has been to write off the first as a jobbing German comic opera composer in the age of Weber and Spohr, the second, as a purveyor of brutalist grandiloquence to the court of Napoleon, treated with awe because Wagner deemed him A Good Thing, and the third as a fluent, original artist of the type that lived too long and wrote too much.

By its very nature the Viking Guide gives each of them a fair hearing, reminding us in the process of the precariousness of operatic fame and the extraordinary, almost dogmatic narrowness, until recent years, of the established repertoire, that inexorable carousel of Carmen, Boheme and Figaro which owed much to the idleness and incuriosity of musicians, managers and audiences.

Defenders of this status quo (and there are still plenty) for whom music neatly divides between Great Composers and interesting Historical Figures, would say that the line must be drawn somewhere. We shall perhaps never witness a revival of Non irritar le donne (1798) by Marcos Portugal, the composer of the Brazilian independence hymn, who wrote his own Figaro opera; of Pavel Wranitzky's intriguingly titled Das Picknick der Gotter (1804) or of John Philip Sousa's Chris And The Wonderful Lamp (1899).

Who, on the other hand, would have imagined the apparition, 20 or 30 years ago, of an authoritative guide which included not merely a synopsis, early performance details and orchestral specifications for Wagner's version of Measure For Measure, Das Liebesverbot, but also a discussion of the work that boldly asserts it to be his most significant early opera? The implicit emphasis of this richly satisfying book is on the way in which enterprising performance, recording and scholarly sleuthing have tugged so much that is enchanting and exciting out of the operatic lumber-room.

This is not a celebration of song, neither does it feature musical examples, but these blocks of impacted information sandwich a wealth of free-ranging critical opinion, some of it decidedly combative. What are we to make, for instance, of a comment like: 'Messager has not enjoyed the revival of interest shown towards Offenbach, but raucousness was not his style'?

In certain cases the pudding seems overegged: is Ernst Krenek, when chips are down, really more important than Domenico Cimarosa? The editors seem to think so, awarding him 11 columns to the Neapolitan master's mere seven.

Only snobs will grumble at the inclusion of Broadway as well as Bayreuth. Frederick Loewe, composer of My Fair Lady, studied, after all, with Busoni. As for the operatic great and good, try Donald Burrows's lavish Handel article or William Ashbrook's warmly appreciative assessment of Donizetti. The whole book sounds a swaggering fanfare in opera's cause.