This is being commemorated throughout the world with cycles of his symphonies this year. I see that Medici.tv is offering the complete symphonies with Christoph Eschenbach and the Orchestra de Paris streamed free (with registration), and Arte will be providing live webcams from the Mahler Festival in Leipzig.
In a recent publication, Resonant Witness, Conversations Between Music and Theology, edited by Jeremy Begbie and Steven Guthrie, there's a fascinating chapter on Musical Time and Eschatology. The point is made that 'Jesus was resurrected not just into the eternal life of God but into a new existence that happens to include such a rich variety of times that created time is not excluded.' To this is suggested that music might be uniquely capable of embodying the 'rich variety of times' that characterise the new creation that has been inaugurated by Jesus' resurrection.
Generally, tonal music is characterised by linear time - you are left in little doubt that the movement or piece has come to an end, to a resolution, to closure. Mahler wrote tonal music but living right at the end of the Romantic period took tonal music to the very limits. And this is particularly evident in the way Mahler used endings, final resolutions, cadences. Traditionally, strong cadences are the means of bringing a piece of music to an end, unless it's Dudley Moore doing a skit on Beethoven's endings!
Mahler sometimes avoids these obvious endings but in order to do so has to resort to different means to establish closure. Take the conclusion to the third movement of the Fourth Symphony, or the final movement of Mahler's Ninth Symphony (for a sensational performance of this see the Youtube clip of Claudio Abbado with the Lucerne Festival Orchestra in which there is silence at the end for well over a minute before the applause). Leonard Bernstein describes this conclusion as 'the closest we have ever come, in any work of art, to experiencing the very act of dying, of giving it all up.' He goes on to say 'But in letting go, we have gained everything.' So this ending proves to be not so much a denial of life but an affirmation of it.
The authors use these two musical examples - both well worth listening to just for their sublime beauty - to explore how a completion need not imply an ending, but rather 'suggest an opening out onto that which is without end or limit - that is, onto infinity or, better perhaps, the transcendent future of God's promise.' They refer to one of the Church Fathers, Gregory of Nyssa, for whom 'the world to come is not a world where we finally "arrive" and all loose ends are tied, but instead is one of infinite progression into the unfathomable mystery of God.'
I may not have done justice to about fourteen pages of fairly dense writing but I think this is the gist of what they're saying. And I have to say I'm taken with it. I wonder what Mahler would have thought!