One of the greatest things you'll see every year at MerleFest is The Hillside Album Hour on Saturday afternoon hosted by The Waybacks.
It takes place on a side stage and started small but has grown each year to be one of the main attractions.
The concept - The Waybacks choose an album/artist to cover in their own style. There are always tons of guests, but they're never announced beforehand. The record isn't announced beforehand either, but they usually give 5 clues leading up to MerleFest for the sleutherists.
Here's an example from the year they did Abbey Road. MerleFest doesn't allow any open recording so you gotta be thankful for what leaks out there...