On May 26, the inaugural Boston Calling music festival closed its doors on an enormously successful weekend. Despite the dreary weather, some 20,000 concertgoers showed up to take in top indie acts like The National, the Shins, and fun. However, co-creator Brian Appel viewed the festival as more of a learning experience. “We saw a lot of things behind the scenes that we want to tweak and make better,” Appel admits. He’ll get a chance this fall, when Boston Calling returns to City Hall Plaza on Saturday and Sunday, this time with a bolder, more diverse lineup that features Vampire Weekend and Kendrick Lamar.

In May, Appel put together Boston’s first major music festival with help from co-founder Mike Snow and The National guitarist Aaron Dessner. The result was an indie-heavy lineup that skewed to the intellectual, with acts like Dirty Projectors and Andrew Bird. There will be quite a different scene this time around, with more traditional rock outfits being replaced by DJs and rappers.

“We know that the audience that lives in Boston in September is a little different, just given the amount of students that come back,” Appel says. “We wanted to go out on a ledge a little bit more in terms of bringing in dance and hip-hop, and we hope the audience responds.”

Audiences will likely respond well to Lamar, arguably the rapper of the year, and Major Lazer, producer Diplo’s hyperactive, genre-hopping dance project. It will also be hard to ignore Solange, who may not have her sister Beyoncé’s status, but makes up for it with her innovation, style and mystique.

Appel and the team of producers made a point not only of improving the diversity of the festival, but also of showcasing local talent. “We have the gumption to call ourselves Boston Calling, so we would be very short-sighted to not look in our own backyard,” Appel says. The festival simultaneously serves as a breaking-out party for Boston-based Bearstronaut—whose huge melodies and danceable guitar lines are reminiscent of the Cure—and a homecoming bash for Cambridge’s own Passion Pit, whose latest album “Gossamer” hit #4 on the Billboard 200 and was acclaimed by critics across the country.

Of course, every festival needs an anchor, and Vampire Weekend fit the bill splendidly. There are very few bands who have exhibited the range, talent, and growth of Vampire Weekend over the last decade; their latest album, “Modern Vampires of the City,” is a triumph of adventurous songwriting, impeccable production and sly lyricism. Furthermore, they have ties to the festival: “We got to know them when they were Orpheum Theatre-size,” recalls Appel, referring to the smaller Boston venue. “They would come through and do smaller shows, and to watch them grow has been terrific.”

Like Vampire Weekend, Boston Calling seems determined to expand its scope and improve with every iteration. Whether or not this weekend's weather will be an improvement on May's, Boston Calling has something new to offer for everyone.

Also playing: Local Natives, The Gaslight Anthem, The Airborne Toxic Event, Wolfgang Gartner, Bat for Lashes, Flosstradamus, Deer Tick, Okkervil River, Flume, Big Black Delta, You Won’t, Lucius, Viva Viva, Royal Teeth