Guest, Andrew. To my mind (as a player myself), the best tunes to try are those that stay in one key and have a strong modal content.
As you're a Bluegrass player, try Turkey in the Straw, Angelina Baker, and Whiskey Before Breakfast for starters. You may have to jump octaves during the tune!.

By coincidence, the other evening I was searching for a couple of old ones that I had around the house, and I unearthed ten, bringing my total to twelve! It's amazing how they multiply when you're not looking.
Most of these are in piano keys, but I found a nice loud one in G.

Splott Man (near Cardiff)