Ragged, jagged Dylan brings it home at Wells Fargo Center

Guessing what Bob Dylan might do next - and pondering why he does what he does - has been a time-consuming avocation for amateur Dylanologists for pretty much the entire half-century of his incomparably inscrutable career.

On Monday, the mysterious man in the white boater hat played the Wells Fargo Center in South Philadelphia, on a double bill that also featured Mark Knopfler, the former Dire Straits frontman who produced Infidels, Dylan's standout album from 1983.

This date on the Never Ending Tour had a more compelling raison d'etre than most. In September, the 71-year-old ur-singer-songwriter released Tempest, his startlingly vital and erratically brilliant 35th studio album, a rugged, deathly piece of work that you might think shares a title, rather ominously, with Shakespeare's last play. (If you did, however, Bob would say you're being silly: "The name of my record is just plain Tempest," he has corrected misinterpreters. "It's two different titles.")

With such a formidable new arrow in his quiver, it would be reasonable to hope that, with the help of his fabulous backing band (whose standouts include string wizard Donnie Herron and guitarist Charlie Sexton) Dylan would be itching to let loose with new songs.

But in doing so, Dylan would be doing what you expected him to. Fat chance of that. Five songs in, while sitting on the grand piano bench he occupied for most of the night - he didn't play a single note on guitar all evening - Dylan did essay Tempest's "Early Roman Kings." That's the powerful blues stomp fashioned after Muddy Waters' "Mannish Boy" that could be about rulers of ancient Rome or a 1970s South Bronx street gang, a song that includes the gnarled, proud proclamation: "I ain't dead yet / My bell still rings."

Indeed it does. And it chimed loud and fairly intelligibly throughout a 15-song set that included a nearly unrecognizable version of "Chimes of Freedom," from the early name-that-Dylan-tune portion of the show. That's when fans, confronted by an unfamiliar melody and a crackly vocal, listened intently for a discernible lyric, then proudly poked their neighbor with the news. Beat you to it: It's "You Ain't Goin' Nowhere"!

With varying degrees of success, "Chimes" and "Desolation Row" were delivered with odd cadences and perverse phrasings by the pencil-moustached Bard, as he kept his doggedly loyal audience on its toes. (And watching closely: there were no video screens to show the notoriously camera-shy Dylan.) The latter was spry and effective, the former robbed of its grandeur by excessive tinkering.

Loyal, but not that large: the upper deck of the sports arena was empty, and the crowd could have snugly fit into a room half the size of the Wells Fargo Center, which holds 20,000. This despite the presence of Knopfler, who joined Dylan on guitar for a frisky three-song run of "It's All Over Now, Baby Blue," "Things Have Changed" and "Tangled Up in Blue."

Knopfler's presence seemed to put a spring in Dylan's step. As the show moved on, and the singer's scorched voice loosened, the music grew more commanding. There were no more Tempest tunes, but a trio of latter day-gems -"Mississippi" from 2001's Love and Theft, and the scrappy "Rollin' and Tumblin' " and ragged, jagged "Thunder on the Mountain" from 2006's Modern Times - benefited from being not-so-familiar that their creator felt the need to turn them inside out.

After "Thunder," Dylan brought it home with authority, standing and blowing his harmonica on a wicked and blistering "Ballad of a Thin Man" and a delightfully sneering "Like a Rolling Stone." Then he returned to the piano - which he played with instinctive, unpolished vigor through the evening - for the closing "All Along the Watchtower" and "Blowin' in the Wind" crowd-pleasers. You've got to give the people at least some of what they want if you want them to come back next time on the Never Ending Tour.

Knopfler opened with a 75-minute set that drew heavily from his double-disc, not-yet-released in the U.S., album Privateering. He performed only one encore song, "So Far Away," as a nod to his 1980s rock-star days with Dire Straits.

Instead, the dexterous 63-year-old finger-picker put the emphasis on his sterling seven-piece band, whose members stretched out on bouzouki, penny whistle and electric guitar in an amalgam of Celtic, Irish and American vernacular styles.

The group stripped down to a punchy three-piece for the highlight "Song for Sonny Liston." The unhurried music was unfailingly pleasant throughout, through the songs' lack of dynamic range and Knopfler's unmodulated spoken-sung vocals grew tedious over time.