From last.fm:

The Billys are a country music band in Anaheim, CA. They give multiple performances daily at the Golden Horseshoe Saloon in Frontierland, Disneyland. While called on their only album as The Billys, on the Disneyland entertainment flyers, they are listed as Billy Hill and the Hillbillies. They are a popular show at Disneyland, known for the comedy, audience interaction, and of course country music. The Billys lineup consists of three different teams, each of which performs on different days. Read more on Last.fm