Mark Snow feat David Duchovny---Paracelsus
Thanks to Julia James for submitting the lyrics
 From "The Field Where I Died" Episode" | Used in: Mulder recites the "Paracelsus" poem from Robert Browning at the very end.
Background info: It was James Wong's idea to add the poem in the episode; Mulder recited lines 596 - 606 of the original poem. The original poem is supposedly more than 4,000 lines long and is published in Robert Browning: The Poems, Volume I. Here is the excerpt)

"...at times I almost dream
I too have spent a life the sages' way,
And tread once more familiar paths. Perchance
I perished in an arrogant self-reliance
Ages ago; and in that act, a prayer
For one more chance went up so earnest, so
Instinct with better light let in by death,
That life was blotted out-not so completely
But scattered wrecks enough of it remain,
Dim memories, as now, when once more seems
The goal in sight again..."