By Jared Feldschreiber

Bob Dylan's live performance on David Letterman last month provided the perfect musical sendoff from one American icon to another.

Dylan delivered a searing and haunting rendition of "The Night We Called It A Day" on the Late Show with David Letterman on May 19. "Beautiful," is how Letterman expressed his delight.

Dylan was channeling Frank Sinatra, as he has done since the release of this year's Shadows in the Night, an album of Ol' Blue Eyes cover songs.

The album is a reminder of a 2004 interview with 60 Minutes, in which Dylan told the late Ed Bradley that he took solace in being able to do things he wasn't able to do in the early parts of his career. He also ruminated on why he continues to tour incessantly.

"Well, it all goes back to the destiny thing," he said. "I made a bargain with it a long time ago, and I'm holding up my end."

"What was your bargain?" Bradley asked.

"To get to where I am now."

"Should I ask who you made the bargain with?"

"With the chief commander."

"Of this Earth?"

"Of this Earth and the world we cannot see," Dylan responded with a laugh.

Dylan grew up in a modest, Midwestern, Jewish home, and his songwriting career reflects a profound understanding of religious tenets. Websites galore - including the very whimsical "Tangled Up in Jews," a reference to a classic 1974 song - have chronicled Dylan's connections to Judaism as exemplified by religious themes in his songs.

While preserving the "holiness" of American roots music, Dylan has constantly expanded his musical oeuvre. He treats traditional music as powerfully as he does a religious hymn. "I find the religiosity and philosophy in the music," Dylan told Newsweek in 1997. "I've learned more from the songs than I've learned from any kind of entity. The songs are my lexicon. I believe the songs."

Dylan's 2012 album Tempest is one example. While the album may have bordered on the macabre, it also deals with the fragility of human experience and the unpredictability of fate. Spiritually, Dylan seeks clarity in an otherwise chaotic, dangerous, and unpredictable world, something he has been wrestling with his whole music career.

He showed his own unpredictability by crooning a jazz standard made famous by Sinatra more than 70 years ago on Letterman. The lyrics come across as something Dylan might have written; it is a song filled with world-weariness and a tinge of wistfulness:

I heard the song of the spheres

Like a minor lament in my ears

I hadn't the heart left to pray

The night we called it a day

Soft through the dark

The hoot of an owl in the sky

Sad though his song

No bluer was he than I

The moon went down stars were gone

But the sun didn't rise with the dawn

There wasn't a thing left to say

The night we called it a day.

In Sinatra, Dylan has found just the singer to exhibit another side of himself: a towering, contradictory, and uncompromising artist. Jakob Dylan once revealed that walking through his father's house would be like sauntering through a historical music museum. One would scarcely be able to find his many Grammy or other music awards.

For Dylan, success is measured by productivity, living up to his true potential, and honing his craft. "We all have our special gift," he sang in his 1968 ballad "Dear Landlord." Even in Martin Scorsese's documentary of his early career, No Direction Home, Dylan billed himself as a "musical expeditionary."

Dylan probed deep within the foundation of American roots music in his 2009 album Together Through Life. There he gave homage to the varied singers of Chicago's Chess Records, which specialized in rhythm and blues, gospel, and early rock-and-roll. In concerts these days, Dylan often sounds like Muddy Waters or the Mississippi Delta bluesmen he idolized as a youth.

It's worth noting that Dylan's exploration of art doesn't stop with music. He is an accomplished artistic welder, painter, and craftsman. His art exhibitions, popularized by "The Drawn Blank Series," which he began in earnest in the early 1990s, have drawn attention worldwide.

Above all, of course, Dylan will continue to be admired as a timeless - and tireless - performer who resolutely maintains a high level of artistic integrity. As he navigates to all corners of the globe, like the roving minstrel he is, one thing remains resolute: this learned Romantic and Beat poet is indeed the master of song. Dylan remains the preeminent purveyor of American roots music, largely stimulated by a strong spiritual understanding of the world.