Bob                                                                                                                                                                    A couple decades before someone anyone ever coined the term “Americana,” Bob Dylan was setting its parameters, creating timeless music that came out of folk traditions that threw in blues, rock and roll, old timey music, gospel and standards.

Of course he’d be the headliner and spiritual guide for a terrific summer tour called Americanarama, paired with a couple of bands that similarly have a foot in many of the same concerns, and who have convered Dylan in the past, Wilco and My Morning Jacket.

As the tour has continued Dylan has also shared the stage with Jeff Tweedy and Jim Jones from both bands, as recently as last week. Tuesday at Meriweather Post Pavilion there was no such collaboration (though My Morning Jacket invited up really early opener Ryan Bingham to help play the Marvin Gaye song long associated with The Band, “Don’t Do It”).

Had there been some sort of breakdown between the bands? Were they getting sick for one another? No, it was probably some sort of time restraint — moving three headliner quality bands across the country and at the limitations of some amphitheaters (off at 11 or else).

Winging it and seeing what happens is what makes the musical event so vibrant. Each band changes up its set every night; some songs work better than others, but some of the missteps set the stage for the kind of pinnacles rare in shows where every song is rote and planned to the light cues.

On a night when it first seemed like the round the clock heat blast had somewhat subsided, Dylan himself was hatless, but in his Spanish detailed matador costume with a scarf tie, spats and big button.

He has a new mannerism on stage, though, a kind of “I’m a little teapot” hand on hip, as he moves back and forth. (Maybe it’s a Flamenco outfit rather than a matador’s).

Still, it’s not as perverse as seeing him give a full concert without once touching a guitar; he had cut way back on it but at least played one on tours in recent years. Now he divides his time in between standing at the microphone with no instrument but the harmonica, or over at a grand piano, standing, and banging out patterns on keys that added spontaneous jags to the music, or led them to musical dead ends, as might happen.

By now he’s got his third lead guitarist of the tour. Duke Robillard started but parted ways possibly because he’s not used to taking orders or not following his own musical muse in solos in the solos he wishes; Charlie Sexton returned to the band for some shows to fill in until a new face, the Canadian Colin Linden jumped on board in Toronto last week.

He was good at doing what being in the band required: Keeping eyes on the boss at all time, framing solos with whatever notes he was plunking on piano, and being ready to bail on a solo whenever Dylan deigns to go back into the song.

Tough gig, but there had been worse Dylan backing bands in the 30 years or so of the never ending tour.

This one begins with unsung rhythm guitarist strumming the insistent chords to “All Along the Watchtower” that the band wouldn’t play until much later. Once assembled they did a strong version of “Things Have Changed” that has been kicking off the shows this summer.

Four songs from the past decade or so, “Love Sick,” “High Water (For Charley Patton),” a breezy “Soon after Midnight” and a bluesy snap of “Early Roman Kings”  gave rise to the possibility of a Bob Dylan show entirely free of songs from the first of the two thirds of his career.

One would almost wish it stayed so when he got to “Tangled Up in Blue,” a song in which mangled up was more the operating phrase , with Bob insistent on starting the verses in the wrong spot, causing a stutter stop to the rhythm.

It only helped make the more recent blues tunes sound better, such as “Duquesne Whistle.” A big drum beat behind “She Belongs to Me” suggested Dylan as if produced by Phil Spector. Still a great song, but missing some of its original tenderness (which one might imagine happening from the writer after nearly half a century has passed).

“Beyond Here Lies Nothin'” was strong, “A Hard Rain’s A-Gonna Fall” stayed close to its original power, though it seemed to have turned into a waltz. “Blind Willie McTell” has turned into a splendid concert highlight with a fresh approach.

It would seem that with “Tangled up in Blue” there would seem no need for “Simple Twist of Fate,” since they seem flip sides of the same record (The way “Like a Rolling Stone” and “Positively 4th Street – neither of which were played – do). But it was better done and less tangled than the other.

“Thunder on the Mountan,” with its references to Alicia Keys and its rollicking velocity is just the right song for an outdoor summer show, and if the final “All Along the Watchtower” seemed rushed, he came out to do a resonant version of “Ballad of a Thin Man” that put to question everything that had happened: Something is happening and you don’t know what it is….

Wilco’s set was generous and rewrding. I have this idea they loaded it with its patriotic songs because of the proximity to D.C.:, starting with “Ashes of American Flags,” and reviving their take on Woody Guthrie’s “Jesus Christ for President.”

“We love this place,” Tweedy said of the venue as they began a version of “Jesus, Etc” able to raise chills. Nels Cline was less a factor overall than I thought he’d be; after a few remarkable solos early in the show he largely held back (but the variety and vintage of guitars never quite stopped; they must travel with a guitar store).

No encore for them nor for Jacket, whose Jim James put on a theatrical cape despite the late afternoon warmth. Here’s a band that has honed a unique sound blending lyricism of exotic ballads, beautifully sung, with a stinging undertow of rock snarl.