By the accident of his dates of birth and death Mahler has provided us with two consecutive years by which to remember him. In 2010 we commemorate the hundred-and-fiftieth anniversary of his birth, in 2011 the hundredth anniversary of his death. This gives us time for a re-assessment – or would do if there were anything left to re-assess. For Mahler has been omnipresent in the concert halls for several decades; every month brings new recordings of the symphonies; and the literature about his life and works is by now immense. Every note has been analysed to death; every snippet of his life snapped by ardent biographers. We have already an excess of Mahleriana. Could it be that we have had an excess of Mahler too?

Mahler once said that he would be appreciated in fifty years’ time. True, the remark was occasioned by jealousy at the critical acclaim showered on the works of his arch-rival Richard Strauss, as opposed to what he saw as the hostile and uncomprehending reception of his own. But he was more prescient than he could have known. It was in the 1960s – some fifty years after his premature death – that he finally became the inescapable presence so familiar to us now. It would no doubt have been bewildering to him that the beginning of the Mahler Era coincided – on a more popular level – with that of the Beatles, but so it was. And he has been with us ever since.

Once Leonard Bernstein, with a panache and chutzpah so suited to this music, had hit the podium with histrionic but electrifying performances nothing was quite the same again. No longer could Mahler be dismissed, as the critics had previously done, as a brilliant writer of Lieder but an indifferent, impossibly grandiose, writer of interminable symphonies. The sound and fury of those gargantuan scores was unleashed at last and – fifty years on – this music addressed to the future found a rapturous reception. Mahler’s time had come at last.

This is not to say that he had ever quite been forgotten. Even in his own time audience reactions were often more enthusiastic than were the critics. In Holland he had always fared much better than in Germany, so when Bernard Haitink took up the baton on Mahler’s behalf this was not Dutch courage – he had a tradition to sustain him too, and offered another, equally persuasive, perspective on Mahler to that of the hyperactive Bernstein. Before long numerous conductors had taken up the Mahlerian challenge, not least amongst them, Pierre Boulez, avatar of musical modernism.

For Mahler had made another (self-serving) prediction – that his music would be remembered when that of Strauss had been forgotten. If this prediction was in an obvious sense off-key – Strauss’s operas and tone-poems have never lacked for an audience – nonetheless Mahler, despite his late-romantic musical language, was seen a precursor of modernism, whereas Strauss was seen essentially as a reactionary. Boulez, for example, has championed Schoenberg and Webern along with Mahler, but never Richard Strauss. Mahler, it seems, paves the legitimate way to the music of the future, whereas Strauss only returns us to the past.

Theodor Adorno’s 1960 book on Mahler preceded the full flowering of the Mahler Renaissance by a good few years, but laid down the parameters along which he was subsequently to be seen. Adorno – excoriator of Stravinsky and champion of the Second Viennese School – saw Mahler as leading the way to ‘the emancipation of the dissonance’ despite the fact that his musical language was ‘primitive’ compared with that of Wagner or Debussy. Indeed, one might think that it is this very ‘primitiveness’, that is, his reliance on tonality, that has helped to secure his popularity over that of his Viennese successors, and there are indeed hints in Adorno as to why that might be the case.

For example, he emphasises how these all-encompassing, world-creating symphonies grab up all kinds of seemingly extraneous material, so that a coherent musical whole is threatened. He makes extensive use of Vulgärmusik – popular songs, dance-material, military marches – thus making him what we now think of as a postmodernist: this is a world where high culture plays perilously with kitsch, where anything can turn into anything, where an innocent song like ‘Frère Jacques’ can be twisted into a funeral dirge, where we (the audience) occupy an uncertain region between tragedy and parody.

Historically, of course, Adorno is correct: Mahler’s music (and personality) were a major influence on his Viennese successors, Schoenberg, Webern and Berg. Indeed, Webern excitedly saw Mahler’s Sixth Symphony as ‘the only Sixth’ – despite the fact that this massive work contrasted starkly with the extreme brevity of his own. But Adorno’s attempt to save the Mahlerian inheritance for the German music of the future foundered on the realisation that that he had been appropriated elsewhere and for other purposes, not least that of salvaging tonality.

Of course, for Adorno, this was all wrong. Mahler, he insisted, was the ‘true socialist realist’ whereas those Russians who had taken him over – clearly, he has in mind here Shostakovich though he doesn’t deign to give his name – offer only a ‘disfigured Mahler’, whereas Alban Berg is the legitimate heir. Adorno’s absolutism is now (hopefully) foreign to us, and we can see that the sons of Mahler are many and various. Often blind to music outside the German tradition, Adorno can find little good to say about the Russian symphony, and fails to mention at all (though he must have been aware of him) the British appropriation of Mahler in the shape of Benjamin Britten (the debt is perhaps most evident in the Sinfonia da Requiem where Mahlerian footprints are everywhere apparent).

The son of Mahler, though, who has had the most popular appeal is undoubtedly Shostakovich, whose symphonies – more uneven in quality than critics now care to admit – have come to rival those of Mahler in numbers of performances and recordings. Gloomy Gustav has been followed by Dismal Dmitri: Weltschmerz and Angst, expressed in tonal form, have filled the concerthalls, whereas the emancipators of the dissonance lie by comparison forgotten and neglected. What Adorno saw as the music of the future is that of a future that has never come.

The Shostakovich symphonies with their cries of despair, their ironies, their flashes of sarcasm, their virulent negativity, their coded messages, not to say their sardonic use of the banal, in every way bear the imprint of Mahler – sometimes uncomfortably so. If you want an approximation to the death-haunted sonorities of late Mahler, of Das Lied von der Erde and the final two symphonies, your best bet is the Shostakovich string quartets – more sustained in quality and more uncompromising in their musical technique than are the symphonies – where all elements of the circus or of playing to the crowd are left far behind, and no consolations are on offer against the certainty of our own extinction.

With both Mahler and Shostakovich we have a curious phenomenon, the one (for Adorno) presenting the soul of man in late capitalism, the other the soul of man under the dark sun of the Stalinist constitution; yet both strike chords with audiences beyond the élite of classical music-lovers in an era when symphonies and string quartets are for the most part a matter for the delectation of a coterie rather than a resource for the many. Mahler’s symphonies, with their relatively accessible tonal language, their enormous forces often used to chamber-music effects (thus making for a dramatic televisual experience), their immediacy of dramatic effect, their very vehemence, like those of Shostakovich have brought them out of the frock-tailed solemnity of the classical ambience if not quite out onto the streets. They at least speak to a much wider audience – indeed, one to whom the symphonies of Haydn, say, where simple happiness is to the fore, are a foreign country.

There is a certain pathos in this. Clearly, Mahler (and Shostakovich) are major composers, but there is a danger of their being done to death, so that other voices can hardly be heard in twentieth century music. Those, for example, of Bartók, Janácek and Nielsen surely too have potential appeal to a wider audience than they now reach. Much of their music shares the visceral quality and immediacy of effect of Mahler and Shostakovich and their language, although very different, is a (more or less) tonal one. And what of Mahler’s – in Adorno’s terms – true heirs? Berg’s Lulu and Wozzeck, for example, for all their density of utterance, have a dramatic power that makes us forget the difficulty of the musical language.

And, easy listening apart, there is a wealth of fine music written in the twentieth century that is available in recordings – though virtually never present in the concert-halls – and enjoyed only by a select, small band of followers. One thinks of those lonely souls who struggled in the wake of Schoenberg (and of Adorno) to write in what they saw as an authentic idiom, only to find that tonality triumphed after all. A temporary moratorium on Mahler would allow these others to have their day in the sun. But this is unlikely to happen until audiences are sated with what is presently on offer. And the reasons are as much commercial as musical. Mahler, like Shostakovich, has proved to have paying power: concert seats are filled, and books about them and recordings of their music sell. We are unlikely to have respite from them for a good while yet.