The last movement is most impressive to me since it sounds like an expression of farewell to the life. Some critics point out this movement was not deliberately orchestrated as the other 3 movements since he had not corrected this movement as he always did. Nevertheless, that might mean his thought and emotion are directly expressed in this movement. It starts with a theme played by 1st and 2nd violin parts in unison. A motif composed of 32nd notes in this theme will be appearing in the extended form throughout this movement. It seems as if a theme of life, more materially, of breathing. The violin solo sings a song of consolation in the background loneliness. The atmosphere throughout the music is separated lonesomeness. The end comes with long diminishend. Viola solo and then cello solo plays a motif of dying made of downward chromatic scale. It ends with the weakest dynamic indication. The last bar has the expression mark of "ersterbend", that means as if dying. Mahler used to use this mark in the other musics like his 2nd symphony but has never put it in the very last bar. This typically shows us what he wanted to express this music.
Claudio Abbado conducted Lucern Festival Orchestra in this video clip. Most famous players were gathering for this performance. It was almost 3 years before Abbado himself passed away. I don't know if he has known of his fatal illness of gastric cancer at this time of performance. His concentration on music may tell us he was already conscious of his own mortality. In some interview or article, he told death was only a phase of existence of life. He seemed to live well through expressing death in this performance. He sometimes smiled at the orchestra performers in the intervals between the movements. In the end, it might be a planned produce, the lighting gradually got dim. He has kept the silence for a couple of minutes. During that silence, he might have wanted the audience to appreciate of the struggle Mahler has made in this symphony. Not shouting something like bravo. It is the most impressive moment in this performance. It is a theme delivered from Mahler to each of us.