WHEN NIETZSCHE was asked in what category he placed his book Also sprach Zarathustra, he replied “Symphonies”, so it was appropriate when his younger contemporary Mahler set a text from it at the heart of his Third Symphony, completed in 1896 (the same year as Strauss’ wordless Also sprach … ). This first attempt to set philosophy to music was the climax of the 120th Proms season last week in a performance by the Leipzig Gewandhaus Choirs and Orchestra (11 September) that more than lived up to its position on the schedule. The three-movement build-up to Nietzsche cast a spell from the horns’ immaculate announcement, as blemishless at its repeat, to the distant, offstage post horn with its promise of a mailbag. The conductor, Alan Gilbert, without the score,