People are picky about music. Of all the genres, the discussion of what is or isn’t authentic bluegrass will always be the subject of heated debate. That’s because people whose grass grows blue are passionate about it. That’s why I like it: Bluegrass is more than a musical genre, it’s a way of life. On Saturday, Sept. 10, an impressive selection of passionate pickers will take the stage for the fourth annual Richmond Bluegrass Festival at Hardywood Park Craft Brewery. On the bill are 21st-century keepers of the early-20th-century flame, Cook County Bluegrass, the River City Band, Only Lonesome, Tara Mills and the Hot Seats. Whether you’re a diehard fan or casual listener, you’ll get a mighty acoustic punch impossible to resist. The blue moon of Richmond festivities runs from noon-10. Free admission. hardywood.com.