Every so often a recording is unearthed that really does possess legendary status and, for Mahlerians, the two premiere performances of Deryck Cooke’s realisation of Mahler’s unfinished Symphony No 10 – issued by Testament Records – are both in that category.

To dub the Tenth Symphony “problematic” would be an immaculate understatement. As Mahler entered terminal decline exactly a century ago, his work on this piece became ever more febrile. Ever superstitious about the mortal danger of writing nine symphonies, he had thought to cheat death by slipping the unnumbered Das Lied von der Erde into his symphonic canon. His superstition, however, turned out to be well placed and his reprieve was brief. The remarkable facsimile produced in 1924 of most of his sketches for the Tenth Symphony reveal not only the failing hand of a man whose heart was fatally infected; for he was evidently sick at heart figuratively too. His emotional scrawlings to his wife are still painful to read. Only two of the work’s projected five movements were completed in full score, but Mahler did leave a clear line of argument, from beginning to end.

There have been numerous attempts to “complete” the work, but it was Deryck Cooke’s performing edition – honed with the help of the Matthews brothers – that proved to the world that this torso was worth exploring at all. Sadly, many of the great Mahler conductors – Tennstedt, Bernstein, Maazel, Jansons – have never conducted any of the editions. Riccardo Chailly, whose fine Berlin recording of the Cooke edition still holds its own splendidly, blames Bruno Walter for this. It was Walter who initially caused the composer’s widow Alma to set her face against any attempt to perform the piece in full; and he who first propagated the notion that all but the (fully scored) first movement of the work should be interred along with its composer. Alma’s mind was changed when she heard a fragmentary performance given by the Philharmonia Orchestra, conducted in 1960 by Berthold Goldschmidt.

Buoyed by this uxorial U-turn, Cooke was emboldened to complete his performing edition, which was duly premiered at the Proms in 1964 by the LSO, again conducted by Goldschmidt. The first commercial recording, by Eugene Ormandy and the Philadelphia Orchestra, soon followed. As one leading Mahlerian after another eschewed the piece, it took a long time for a meaningful performing tradition to develop. Advocacy from Simon Rattle and James Levine, as well as Chailly, slowly broke the ice and the sheer beauty of this exquisitely symmetrical and radical work has won a devoted, wider audience.

Now, thanks to Testament, many of us can hear, for the first time, both of those Goldschmidt recordings, along with an exploration by Deryck Cooke of the thematic source material from which he drew his performing edition. These three CDs are revelatory, not only because of the manner in which one senses Goldschmidt’s own journey of excited exploration, but also because, looking back from the vantage point of 2011, we realise the true significance of what we now hold in our trembling hands: the only extant recording of the world premiere of a Mahler symphony. Even by Testament’s remarkable standards, this is an achievement indeed.

Michael McManus