Local post-rock veterans Grimace Federation have certainly gone through many configurations over the years. Long gone are the days of their arrival at live performances as a sextet, lugging around a massive vibraphone, but with their current, more minimalist setup as a trio, the band continues to move forward, experimenting and evolving the group’s sound. This past July, Grimace Federation shared a sample of this progression in “The Measure In Mixture,” from their upcoming LP, and you’ll be able to hear more from it this evening at Union Transfer when they open for the Yoni Wolf-led indie rock outfit Why? and Minneapolis, Minnesota’s Dessa. Union Transfer, 1026 Spring Garden, $16, All Ages - Alexis V.