Bob Dylan plays harmonica with his Band while performing at Bayfront Festival Park in Duluth, Minn. Tuesday July 9, 2013 during a stop on the Americanarama Festival of Music. (CLINT AUSTIN/AP)

What is Americana, anyway?

The genre tag is applied to rock bands that merge American roots music — country, blues, R&B — with modern, radio-friendly flourishes. The stylistic waters can get muddy, though. Songs can evoke the music of Woody Guthrie and also U2’s “The Joshua Tree.” Bands might augment wood-grain riffing with flourishes on loan from German experimental music of the late ’70s. Americana is not necessarily traditional, and the nostalgia does not stop at regional or national borders.

In the case of the Americanarama Tour, the definition could boil down to simply meaning that Bob Dylan likes your band — or likes that your band is evidence of his music’s enduring influence — and has decided you should accompany him on the road.

On Tuesday night, Americanarama arrived at Maryland’s Merriweather Post Pavilion. The bill has shifted slightly from city to city, but the shows are anchored around three acts: My Morning Jacket, Wilco and Dylan, each of which is capable of packing a barn-style venue on its own.

They have been brought together seemingly at Dylan’s behest, with the opening acts ceding the spotlight for the chance to tour with an idol. But while other dates on the tour have seen some impromptu duets and familial banter, Tuesday’s show was slim on inter-band camaraderie.

Even if they weren’t palling around in public, Wilco and My Morning Jacket benefited from being in close proximity to each other. When you’re sandwiched onto a triple-headlining bill with your idol, there’s no time to play the snoozy cuts from your sixth record.

Formed in Kentucky during the late ’90s, My Morning Jacket plays a spacious strain of Southern rock. Often, the band sounds like a boombox blasting Lynyrd Skynyrd from the bottom of an empty swimming pool.

Singer/guitarist Jim James is a thoroughly theatrical frontman, frequently ditching his guitar to don a cape and stalk the stage with a sampler swinging around his neck. On the band’s closing song, “Victory Dance,” he picked up a saxophone for a final bombastic blowout. However you feel about MMJ, it is not an easy act to follow.

Wilco had that duty Tuesday. The band, led by Jeff Tweedy, began in the mid-’90s as a country-rock group with punk underpinnings but in the past decade has swung toward experimental pop. Its set alternated between its most and least thinky tunes — pivoting between lighter-wavers from the early era, such as “I Got You (At the End of the Century),” and newer, noisier fare, such as “Bull Black Nova,” that could rival My Morning Jacket in terms of stage volume.

There’s a clear kinship between Wilco and My Morning Jacket. Both bands began as roots rockers but became more successful as they expanded their sonic scope. Both also have taken heavy inspiration from Dylan, from both his songwriting and his ability to shift between identities and styles.

Dylan, on the other hand, seemed a world removed from his tour-mates.

The singer, now 72, performed a set of music mostly drawn from his last decade’s worth of studio albums, in which he largely favors traditional folk and blues sounds. The years have rendered his voice craggy and muppet-like, and it was sometimes hard to parse his famous lyrics. There were times when the audience cheered mid-song, having only recognized a rejiggered classic such as “A Hard Rain’s a-Gonna Fall” from the chorus.

Dylan seemed energized, though. He moved between piano and harmonica, giving cues to the band and smiling slightly between verses. Stage banter is not Dylan’s thing, and he never paused between songs to gab about his age or wobbly gait or to acknowledge the other bands on the bill. That silence works to his benefit, though. The total vacuum of personal information created the perception that he was somehow slightly more than human — an ageless gargoyle pacing between two flickering torches that had been set up on either side of the stage. Those torches stayed where they were, symbolically and otherwise.

Leitko is a freelance writer.