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At a festival where two out of three headliners were coming off of the release of their second albums, the Avett Brothers were positively grandfatherly. Though the group only truly broke into the mainstream with the release of “I and Love and You” in 2009, Scott and Seth Avett put out their first EP as the Avett Brothers in 2000, when Alabama Shakes frontwoman Brittany Howard was only 12. Perhaps the band’s maturity partially explains why, during their first few songs on Friday evening, the crowd scarcely made any noise at all. Though City Hall Plaza appeared filled to capacity—as it generally is for Boston Calling’s last Friday slot, the longest and thus most important set of the festival—the audience seemed to have been lulled into placidity by Seth Avett’s gentle acoustic guitar and vocals on “Bring Your Love to Me,” the track with which the band began their set. That the crowd was so subdued is not a judgment on the Avett Brothers’ popularity but a testament to the power of the song—which sounded even more beautiful than its studio recording for all the slight imperfections of live performance—but it also illustrates a difficulty that the Avett Brothers must navigate in their performances. The group rises to equally great heights on their slow, romantic tracks as they do on those full of strumming, bluesy energy, and to unite the those two distinct modes into a coherent live performance is no mean feat.

This struggle was not without its casualties on Friday night: During “November Blue,” Scott Avett’s turn to perform acoustically and the band’s most exquisitely heartbreaking track, one could hear a buzz of conversation emanating from the audience. To fill an outdoor space with a single voice and a single guitar is challenging at the best of times, and this early in the set the crowd seemed restless, all too ready for hand clapping and foot stomping. Fortunately, at all other times the Avett Brothers managed to release the crowd’s energy with the learned skill of a decade of touring: Without missing a beat, they transitioned from “Bring Your Love to Me” into “Talk on Indolence,” a frenetic tongue twister of a song that had the crowd jumping up and down as a mass in time with the band’s own leaps about stage and threatening to collapse the VIP platform.

Throughout their performance, the Avett Brothers executed seamless transitions: Their set felt more like a continuous, hour-and-a-half-long exploration of their repertoire than a collection of distinct songs. Even those moments between tracks—most prominently a bold fiddle solo from their touring violinist, Tania Elizabeth—fitted solidly into their set and maintained the level of excitement they had established. As the night wore on, the band members seemed to feed off of one another’s energy, though most mere mortals would probably have been exhausted by jumping about as much as they did; cellist Joe Kwon in particular head banged his impressive mane with ever-increasing intensity. The band reached its performative height toward the end of its set with “Kick Drum Heart,” a track that could give a cramped basement bar the atmosphere of Lollapalooza. Toward the end of the song, Scott helped Seth down off of stage and then followed his brother into the photography pit, to the screams of the fans at the front of the audience, and the pair finished performing the song there—only to move into a hard rock, electric guitar-heavy interlude when they returned onstage. It was at that point obvious that the Avett Brothers had managed to win over a relatively difficult crowd by the sheer force of their energy.

By the time they left stage for good, the Avett Brothers had accomplished their trickiest task yet: They had at last, during “Murder in the City,” convinced the crowd to stay enraptured in its silence, almost reverent in the face of the track’s elegant sorrow. Whether because they stood out somewhat awkwardly among a lineup of neophytes or because their stylistic range far exceeded of most of the weekend’s other artists, the Avett Brothers were presented with a challenge in performing at Boston Calling. And, as can hardly be surprising for a band so renowned for their live performances, the group rose to that challenge majestically, stomping and strumming with passion and fervor late into the North End night.

—Staff writer Grace E. Huckins can be reached at grace.huckins@thecrimson.com.