When Nat, her best friend Jess and singing-star wannabe Harper sing together, their harmonies bring down the house. For Nat, the experience sparks a driving new desire to perform. But when the girls form a trio and enter a contest for a chance to play at the Tall Grass Music Festival, Nat finds that harmony, musical and otherwise, is hard to maintain. Her bandmates almost never agree, her new boyfriend starts behaving more like a non-boyfriend, and the trio's famous-musician mentor doesn't even like the way Nat breathes. Every day, Nat's dream of performing at Tall Grass seems farther away, and she questions whether she has what it takes to get there.