Fans will be far from “Unconsolable” when the X Ambassadors, along with Rachel Platten and Jukebox the Ghost, headline Musikfest at 7 p.m. Aug. 5 at the Sands Steel Stage. The X Ambassadors, formed in 2009, have gained a following for their smooth vocals and elegant melodies. The band’s “Renegades,” from 2015’s full-length debut album, “VHS,” has become an international hit, peaking at No. 17 on the Billboard Hot 100 and topping other Billboard charts. Among the group’s other popular singles are “Unsteady” and “Jungle” from “VHS,” and “Unconsolable,” from the “Love Songs Drug Songs” EP. The band is: brothers Sam and Casey Harris, Noah Feldshuh and Adam Levin. Rachel Platten has had the Top 10 hits, “Stand by You” and “Fight Song.” Jukebox the Ghost has appeared on “The Late Show with David Letterman.”