OK, look, maybe this is not everybody's bag, but this is great stuff. Bernstein doing Part I of Mahler's 8th. Unfortunately, these are not continuous or complete clips, just excerpts. Additional unfortunateness: I tried to do a YouTube embed on this but got stymied at one step of the process.
Part 1 of Mahler's 8th is the "Veni, Creator" put to music.
As an added bonus, same performance, the very end (the "Chorus Mysticus," which has been linked ad nauseum by me before):
Extra super special bonus: an excerpt from a documentary on Bernstein, Mahler and the Vienna Symphony.