The Wailin’ Jennys have been stalwarts of the folk-pop scene since their founding in 2002, and this Saturday they bring their precise harmonies and energetic Americana inflections to the Barre Opera House stage. Soprano Ruth Moody, mezzo Nicky Mehta and alto Heather Masse weave their voices and their instruments into one impeccable, rootsy sound. It serves them well when they play from their Juno Award-winning albums 40 Days and Bright Morning Stars, as well as from Firecracker, the album that charted for more than a year on Billboard. Audience members will hear the band’s hits, alongside traditional folk songs and numbers by the likes of Tom Petty and Dolly Parton.