Listening to the electronic beats of MGMT’s CDs “Oracular Spectacular,” “Congratulations” and their EP “Time to Pretend,” one might wonder what Benjamin Goldwasser and Andrew VanWyngarden do onstage besides sing and perhaps play recordings of synthesized sounds. However, at their Aug. 12 show on the Burlington Waterfront, MGMT proved that they do a whole lot more live than hit a play button. It was a mild night when MGMT walked onstage to face an excited crowd and the sun setting over Lake Champlain. Goldwasser and VanWyngarden, as well as Matthew Asti, James Richardson and Will Berman from their live band, who joined them in the studio for “Congratulations,” showed their musical chops playing guitar, keyboards, bass, drums and singing to a sold out crowd of 4,000 on Aug. 12. In front of a huge screen playing just the sort of psychedelic images you’d imagine, they played songs from both of their full-length albums, interspersing fast-paced, crowd-pleasing favorites “Electric Feel,” “Time to Pretend” and “Kids” with slower tracks featuring long, spacey beats. This caused a strange dynamic of a fairly passive crowd that would only become completely focused when a popular song would start to play. Perhaps the occasional sense of apathy from the crowd can be attributed to the likelihood that much of the crowd probably only knew their most popular songs well. That, or the consumption of alcohol that undoubtedly occurred. The concert had vendors selling UFO, IPA and Harpoon beers. It wasn’t, however, because MGMT didn’t play or sing well. Despite the slightly apathetic crowd, MGMT’s well-executed and creative performance of older songs such as “Weekend Warriors” and the title track from “Congratulations” made me wonder why so many people only know a few of their older songs. While it was refreshing to see that such an electronic band can actually play instruments, and the concert was pretty fantastic overall, the boys of MGMT may have taken it a bit far with the encore. Having already played their three most popular songs, the highly demanded encore was little more than jamming. Had they held out and played “Kids” or “Electric Feel” last, the concert might have ended with more punch. Having seen MGMT play to a crowd of mostly teenagers and young adults, decked out in hipster neons and 80s-influenced threads that bordered on ridiculous, “everyone looks awful,” UVM junior Xana Raymond said. It’s difficult to imagine seeing them play in a different setting. The show was part of the 2010 Maritime Festival and, with people lounging on the grass and crowding up front, it definitely had the laid-back vibe of a festival — which felt like the perfect setting to listen to the hipster-youth synthpop that is MGMT.