It's Bach - by a nose!

One of the fascinations of a new edition of Grove is the way it plots how musical fashions change: how composers once highly extolled fall out of the public's favour and others, once neglected, replace them. The figures for the lengths of the entries for individual composers quoted below cannot be taken literally, as if they belonged to a kind of musicological league table, since some entries owe part of their length to the catalogue of works. A composer who left as many songs as Schubert is sure of a sturdy total.

Even so, comparing the new production with the very first Grove, published between 1878 and 1889, and then with the Eric Blom edition of 1954 (the fifth in the series), and then Stanley Sadie's first New Grove of 1980, tells an intriguing story. Nowhere are the contrasts more telling than in the case of JS Bach. In the first Grove, Bach merited just six pages as part of an extended section on the whole Bach family, complete with family tree. This was not because Sir George Grove was impervious to the composer - he wrote elsewhere of his "burning genius". Yet he still got only six pages, where Carl Maria von Weber was given 42 and Mendelssohn 58. By 1954, Bach's allotment had reached 28: still way behind Beethoven, Mozart and Liszt, but gaining. In the new edition, it is 74, a nose ahead of Beethoven.

Mendelssohn is another instructive case. This latest Grove closely analyses the ebbs and flows in his reputation. After his death (1847), it says, his music and his memory came to be so idealised that a reaction later set in. George Bernard Shaw summed it up, complaining of "his conventional sentimentality, and his despicable oratorio-mongering". His allotment dwindled to 32 pages in 1954 and to 24 in 1980. But today's Grove gives him 36, and this carefully pitched accolade: if he missed greatness, he did so as HL Mencken suggested, "by a hair".

Compared with us, of course, Sir George, a civil engineer and builder of bridges for whom music was a private passion rather than an employment, was deprived. By dying in 1900 he missed a great deal of Mahler and all of Shostakovich. Yet some omissions from the Grove of 1878-89 are startling. In an admittedly hurried trawl I failed to find Tchaikovsky (1840-93), even when looking him up under the once-popular spelling that started his name with a C. There are only two pages of Brahms (1833-97) and, astonishingly, just three of Berlioz, who had died in 1869. Berlioz has 37 pages now: one more than Mendelssohn, who sometimes disparaged him.

Because the new edition is not yet available, the only counts I have been able to log are those I have begged from the publishers. So I cannot be sure, but I bet Berlioz's hero Spontini doesn't do nearly as well now as he did in Sir George's first version, when his ration fell only just short of Haydn's. The text this time, anyway, is dismissive: as a composer, he was "ephemeral", it judges, though important as the first conductor to make use of a baton.

I thought there might be a similar pattern for Hummel, to whom some once accorded near-Beethovenian status, but Sir George was not fooled. "The classic of the pianoforte - but a dull classic," that first edition announced, restricting him to one column. Again, the new edition is kinder: his music, it says, "reached the highest level accessible to one who lacked ultimate genius". So encouraging, don't you think, to have such judgments available in the case of those composers who, like Hummel, leave one very much in two minds?

Take Francis Poulenc, a composer I mostly love but would sometimes like to reach down the years and strangle because of the way some of the bigger works slip into flippancy. On the whole, 21st-century Grove is forgiving, as I would wish it to be. "If Poulenc is not quite a Schubert, he is among the 20th century's most eligible candidates for the succession," it says. One would have to feel pretty grudging to quarrel with that.

Related articles:

But where's the music?
Alan Rusbridger ventures into the online version

The book of everything
For music lovers, the New Grove dictionary is Wisden, Britannica and the Bible rolled into one. Next week sees a momentous event, the first new edition for 20 years. Here Charlotte Higgins talks to the people behind the 29 volumes