British folk-rock band Mumford & Sons will make its area debut in September at the Jazz Aspen Snowmass Labor Day Festival. Also added to the lineup were soul-rock groups Michael Franti & Spearhead and Vintage Trouble.The two acts were added to a previously announced lineup that includes singer Kid Rock and country-pop band Sugarland, both of whom are making their first local appearances, as well as the classic-rock group the Steve Miller Band and New Orleans jazz-funk band Trombone Shorty & Orleans Avenue.The festival, in Snowmass Village's Town Park, is set for Aug. 31 through Sept. 2.Mumford & Sons will headline on Sept. 1. The London-based quartet's debut album, 2009's "Sigh No More," hit No. 1 in Ireland, Australia and New Zealand and No. 2 in the U.K. and the U.S., was nominated for two Grammy Awards and earned a Brit Award for British Album of the Year. At the 2011 Grammy Awards show, Mumford & Sons joined Bob Dylan and the Avett Brothers in a performance of Dylan's "Maggie's Farm."Opening for Mumford & Sons will be Trombone Shorty & Orleans Avenue. The group, which is led by trombonist/trumpeter Troy "Trombone Shorty" Andrews and mixes R&B, New Orleans brass band, rap and more, sold out an appearance in December at the Wheeler Opera House.Aug. 31 features a bill of Sugarland and the Steve Miller Band. Franti, who has performed three times at the Labor Day Festival including at last year's event, will open for Kid Rock on Sept. 2, with Vintage Trouble kicking off the day.A limited number of three-day passes are available for $175. Single-day tickets go on sale Friday. Tickets can be purchased by calling 866-JAS-TIXX, online at www.jazzaspensnowmass.org or at the Belly Up box office.