Which Mahler symphonies?

What you were hearing were excerpts from Mahler's First and Second Symphonies. Many of the melodies reappear in his "Lieder eines fahrenden Gesellen" (Songs of a Wayfarer) and some from his collection of "folk songs" called "Des Knaben Wunderhorn" (The Youth's Magic Horn). All of these are thrilling in their own right and well worth listening to.