Good stuff, Maestro! :)
He also used another poem, Bimm Bamm, which attempts to recreate the sound of church bells. This was inserted into his Third Symphony as the fifth movement. The chorus is supposed to be angels singing in heaven.
Even when Mahler is working with beauty and innocence, he cant help letting his sardonic side come out, and at 2:30 he lets it loose. But he resolves it beautifully with the soprano voices holding the last note.