“I’m not afraid to dance, and I’m a full grown man,” Beck said late in his set. Beck, who was preceded by Sharon Van Etten and Tame Impala, had finally urged the crowd into at least a state of modest dance. This was still Boston, after all. It took all the talent and swagger of the Grammy-winning singer-songwriter to get the folks moving and grooving. What Beck might have lacked in physical stature, he sure made up for in musical range and, yes, dance moves. Friday was the first night of Boston Calling, the three-day festival held twice a year right outside City Hall, running Friday night and all day Saturday and Sunday. This year’s festival will host My Morning Jacket, Ben Harper, the Pixies, and many more in the days to come. There is a discovery/searching part of any festival, usually in the first hour or two. Festival goers wandered around the red-bricked city square gazing at all the sponsors. As they dipped their toes into the pavilion for the first time, so did Van Etten. The Brooklyn-based electric folk artist treated the growing crowd to cuts from across her work, including the unreleased “All Over.” Van Etten used basic arrangements, but her lingering guitar and voice cut through the square making it a peaceful first hour or so of wandering. Eventually, there is a settling phase in any festival. The wanderers rooted themselves for a while. Aussie psychedelic Tame Impala and its warped, ’60s-inspired sound helped settle the crowd. Tame Impala sent wave after wave of rolling bass and reverb-heavy vocals, and most of the crowd was happy to let it wash over them. Finally, Beck arrived. He was the ’90s come alive. He was a genre-blending tongue twister. He danced in and out of a void of his own creation. Though cuts from his Grammy-winning Morning Phase made up a chunk in the middle of his set, pulling out the acoustic guitar for “Blue Moon,” “Heart Is a Drum,” and a few others, Beck frequently—and rightfully so—pulled from his ragtag past. Filling most of the square at this point, the crowd reacted with enthusiasm to hits like “Loser” and closer “Where It’s At.”