When the Americana Music Festival and Conference rolls around Sept. 17-21 in Nashville, you can bet on there being plenty of guest sit-ins during Americana Showcase sets. With a large portion of the genre's biggest stars either living in Nashville or in town for the Americana Honors and Awards Show, guest performances are rampant. But some artists performing at Americanafest 2014 don't have to wait for guests to get a group of established Americana stars on stage together. It's just part of their band. These 5 Americana supergroups are guaranteed to provide the star power bang for your buck.