An afternoon thunderstorm temporarily halted the annual Buzz Beach Ball on Saturday at Sporting Park. Nonetheless, most of the 23,000 or so fans who attended endured the rain and the heat and stayed until the festival ended well into early Sunday morning.The delay pushed back set times more than an hour. Headliner Alt-J was scheduled to perform from 10:30 until to 11:45 p.m. but didn’t start its 75-minute set until about 11:55 p.m. Still, at 1 a.m., the stadium was nearly as full at 1 a.m. as it was all day.Alt-J is a British rock band with only two albums in its catalog, yet it appears to be on the verge of graduating to arena status. Their music is a mix of indie, electronic, pop and prog rock that can get folkie when it feels like it. In other words, it’s hard to pin down and sounds +as if it is+ derived from a few eras.The band is led by Joe Newman, who has one of those love-it-or-loathe-it reedy voices that defines its sound. (It reminds me of Roger Hodgon’s Hodgson of Supertramp, who, to my ears, sounds like more of an influence on Alt-J than Radiohead.)For a four-piece, they Alt-J can arouse a dynamic, hypnotic vibe, that, after 45 minutes or so, can start to become monotonous. Granted, the clock was approaching 1 a.m., which was more than 10 hours after the start of the festival, sponsored by radio station KRBZ (96.5 FM), but some people in the seats had fallen asleep.They opened with “Hunger of the Pine,” a languid and trippy track from “This Is All Yours,” the band’s second album, which was released in September. Next came “Fitzpleasure,” a track infused with some R.E.M. guitar jangle +that was+ the first single from their debut +album+, “An Awesome Wave.”,” a track infused with some R.E.M. guitar jangle. They covered Bill Withers’ “Lovely Day,” +which is+ a hidden track on “This Is All Yours,” and +played+ a couple of instrumentals. It The set list also included “Tessellate” and the threefour other singles from “Wave,” including “Tessilate” and “Breezeblocks,” which closed the show and sent the crowd on its way, groggy but happy.The rest of the show was a mix of music that you hear on alternative radio. Awolnation preceded Alt-J on the main stage, delivering an hour of throbbing electronic/industrial -pop, a sunnier version of Marilyn Manson or Nine Inch Nails that turned the floor of the stadium into a thrashing mosh pit. The Los Angeles band, which, is fittingly is on Red Bull Records, is led by Aaron Bruno, who, like a hopped-up carnival barker, cajoled the big crowd into several frenzies.Taking Back Sunday made the most of its 45-minute main stage set. The New York band is led by the swashbuckling Adam Lazzara, a lead vocalist with D’Artagnan looks and weightlifter biceps. Their music is a familiar blend of punk and power pop and bits of pop metal. The set list included “Makedamnsure” and “Liar.”Glass Animals haves only one album in theirits discography, but it received a headliner’s ovation during theirits set on the main stage. They’re a British band that plumbs a few genres to concoct a sound that sways from soul and psychedelia to electronic indie-pop. TheirIts set list included “Walla Walla,” “Gooey” and “Toes.”Milky Chance, an indie-folk/rock/electronic duo from Germany, played an early post-storm set on the main stage. Clemens Rehbnein has a gruff, laconic voice that suits his band’s music, which bears some catchy hooks and melodies, but could use a little craftwork.The second stage was set up at the end of the field (or “pitch,” to be exact) opposite the main stage. Set times alternated so that one stage re-started about five minutes after the other ended. It included performances from Zella Day, who has a little Florence and the Machine thing going; and Hanni El Khatib, who does the gritty, swampy indie rock-blues thing with some flair.The two second stage closing acts on the second stage were Misterwives and Robert DeLong. Misterwives, led by the dynamic Mandy Lee, a singer with some Feist in her pipes who showed off her fitness by dropping and giving the crowd five or six push-ups, military style. Then her sax player donned a cape and did a cartwheel. The band’s music is a whirlwind of styles, almost manic to a fault, but it generated several long and loud ovations.With much dexterity, DeLong did the one-man DJ/musician thing, fusing looped and recorded sounds with live music and live vocals. The crowd sang -along robustly to some of his poppiest songs.Alt-J would take it from there into Sunday morning, concluding a festival that turned into one long day, night and early morning at the beach.To reach Timothy Finn, call 816-234-4781 or send email to firstname.lastname@example.org. Follow the Back to Rockville blog on Twitter: @kcstarrockville.