The entire 7th symphony is a gradual accelerando from beginning to end, taking one from the tragic 6th symphony and dumping them on the doorstep of the life-affirming 8th; the symphony that Mahler himself stated as being his most important and greatest. In the finale of M7, Mahler makes fun of himself and the entire late romantic genre. And by the way, the "Song of the Night" business was not dubbed by Mahler.
Mahler referred to the finale of M7 as being "a ray of sunshine in C-Major", and had the Czech Phil. jump to the finale when his wife entered the hall during one of the final rehearsals. I wonder what she made of it ?!?