Mentioned by Nashville 4 days itinerary
4 Days In Nashville: Trip Itinerary and Visitor’s Guide
"For this particular Nashville itinerary, the 3 or 4 attraction FLEX pass, can save you a few dollars on entrance to the Country Music Hall of Fame and Studo B tour, the Hatch Show Print tour, and the tour of Andrew Jackson’s Hermitage. If you choose to also visit some of the other attractions (mentioned below) that aren’t officially part of this Nashville itinerary, you could save around $35 USD with the 6 attraction FLEX pass."