At the time of Mahler's death, the composition was substantially complete in the form of a continuous draft, but not fully elaborated or orchestrated, and thus not performable.

Perhaps as a reflection of the inner turmoil he was undergoing at the time (Mahler knew that he had a failing heart and that his wife had been unfaithful), the 10th Symphony is arguably his most dissonant work.

Mahler then started on an orchestral draft of the symphony, which begins to bear some signs of haste after the halfway point of the first movement.

Mahler was at the height of his compositional powers, but his personal life was in complete disarray, most recently compounded by the revelation that his young wife, Alma, had had an affair with the architect Walter Gropius.

Mahler sought counseling from Sigmund Freud, and dedicated the Eighth Symphony to Alma on the verge of its successful première in Munich in a desperate attempt to repair the breach.

Arnold Schoenberg famously expressed the opinion that no one could possibly write a Tenth Symphony without being close to the hereafter (see Curse of the ninth); and a mistaken report led Richard Specht to suggest Mahler wanted the manuscript burned after his death.

The facsimile made evident that the stress of Mahler's final year had not adversely affected the composition, and that the draft contained passages of great beauty.

Alban Berg was enlisted to proofread the work, but his suggested corrections were never incorporated, while at the same time some unauthorised changes were introduced, possibly by one of the conductors of the first two performances, Franz Schalk and Alexander von Zemlinsky.

This version has since received its first performance in nearly 100 years in December 2019 with the Hong Kong Philharmonic Orchestra conducted by Jaap van Zweden, who later recorded it.

Figures such as Shostakovich, Schoenberg, and Britten (all of whom had been considerably influenced by the works of Mahler) refused, and instead the task was taken up by musicologists: early attempts at realising the entire work were made in America by Clinton Carpenter (completed 1949, subsequently revised 1966), in Germany by Hans Wollschläger (1954–1960, withdrawn), and in England by Joe Wheeler (1953–1965) and Deryck Cooke (1959–1960, 1966–1972 and 1976).

Sincerely yours, Alma Maria Mahler[5]Cooke's revised and completed version, conducted by Goldschmidt, was premièred at the Proms on 13 August 1964 and recorded soon after.

After Alma's death in December 1964, her daughter Anna allowed Cooke access to the full set of manuscript sketches, many of which had not been published four decades earlier.

The view has been expressed that much of this process of recomposition gives the impression that Carpenter has effectively written his own symphony using Mahler's as a basis.

Wheeler's interventions are at the opposite end of the spectrum to Carpenter's, and he is less interventionist even than Cooke: he only makes additions to the score where performance is otherwise impossible.

The version by Samale and Mazzuca was commercially released in 2008 on Octavia Records, through Exton from Japan, with Martin Sieghart conducting the Arnhem Philharmonic Orchestra.

[11] Described as a "reinvention of the draft", this version was premiered under Carvalho's direction in June 2014 at the 37th International Music Festival of Paços de Brandão.

[13] A project to recompose and recontextualise the first movement using samples and electronic effects was completed by Matthew Herbert and released by Deutsche Grammophon in 2010.

The short movement fails to end in limbo though, as after a brief recapitulation a sudden harp arpeggio and gong stroke pull the rug out from under it; it is consigned to perdition by a final grim utterance from the double basses.

This may be a reference to a funeral procession that Mahler once observed: on February 16, 1908, while staying with Alma in the Hotel Majestic on Central Park West in New York City, the funeral cortège of Deputy Fire Chief Charles W. Kruger (whose death in the line of duty inspired the creation of the Manhattan Firemen's Memorial) stopped below their hotel window.

The introduction to the fifth movement re-enacts this scene as a rising line on tubas supported by two double bassoons slowly tries to make headway and is repeatedly negated by the loud (but muffled) drum strokes.

The music of the flute solo that was heard after the introductory funeral scene can now return to close the symphony peacefully, and unexpectedly, in the principal key of F♯ major.

Simon Rattle's 1980 recording with the Bournemouth Symphony Orchestra gave the former percussionist an opportunity to make some pointed revisions, most noticeably giving prominence to the military drum in the fifth movement, which is played as loudly as possible without being muffled or dampened.

Some conductors, notably Hermann Scherchen, Leonard Bernstein, Bernard Haitink, Pierre Boulez, Michael Tilson Thomas, Rafael Kubelík, Václav Neumann, Claudio Abbado, Klaus Tennstedt, Lorin Maazel and Gennady Rozhdestvensky have chosen to perform and record just the Adagio, since they interpret it as the only movement completed by Mahler himself.

In 2011, to mark the centenary of Mahler's death, Testament Records released a 3-CD set featuring Cooke's BBC lecture, the 1960 studio performance of the incomplete version as well as the 1964 world premiere conducted by Goldschmidt.