Symphony No. 10 was written in the summer of 1910, and was his final composition. At the time of Mahler's death the composition was substantially complete in the form of a continuous draft; but not being fully elaborated at every point, and mostly not orchestrated, it was not performable in that state. Only the first movement is regarded as reasonably complete and performable as Mahler intended. Perhaps as a reflection of the inner turmoil he was dealing with at the time (Mahler knew he had a failing heart and his wife had committed infidelity), the 10th Symphony is arguably his most musically dissonant work.
Mahler started his work on his Tenth Symphony 07-1910 in Toblach, and ended his efforts in September the same year. He never managed to complete the orchestral draft before his premature death at the age of fifty from a streptococcal infection of the blood.
Mahler's drafts and sketches for the Tenth Symphony comprise 72 pages of full score, 50 pages of continuous short score draft (2 pages of which are missing), and a further 44 pages of preliminary drafts, sketches, and inserts. In the form in which Mahler left it, the symphony consists of five movements:
The parts in short score were usually in four staves. The designations of some movements were altered as work progressed: for example the second movement was initially envisaged as a finale. The fourth movement was also relocated in multiple instances. 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. He had got as far as orchestrating the first two movements and the opening 30 bars of the third movement when he had to put aside work on the Tenth to make final revisions to the Ninth Symphony.
The circumstances surrounding the composition of the Tenth were highly unusual. 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 counselling from Sigmund Freud, and on the verge of its successful première in Munich, dedicated the Eighth Symphony to Alma in a desperate attempt to repair the breach. The unsettled frame of Mahler's mind found expression in the despairing comments (many addressed to Alma) written on the manuscript of the Tenth, and must have influenced its composition: on the final page of the short score in the final movement, Mahler wrote, "für dich leben! für dich sterben!" (To live for you! To die for you!) and the exclamation "Almschi!" underneath the last soaring phrase.
Mahler occasionally used a five-movement structure for his symphonies rather than the more traditional four-movement structure, and for the Tenth he devised a convincing symmetrical structure with two large slow movements enclosing a core of faster inner movements, at the very centre of which is the deceptive Purgatorio movement.