In answer to your wish for a description, it's called "Carl and Sierra playing Cherokee Maggie." Takes place at Sierra's house. They're sitting side by side on a sofa, Carl in his 30s? (I'm no judge of age) and Sierra ordinary-attractive in old clothes and long dirtyblonde hair perhaps age 15? She plays a Dreadnought-style guitar, he an F-5 style mandolin.
The tune is a three-part minor gem, with no (to me) detectable traditional antecedents, much as described by others above. Very intricate in the Fleck style. Her guitar is mellow-toned and a little down in the (non-) mix. Just one of those haphazard informal takes.
Carl's a deft strong mandolin player with a sharp quick attack, but it is Sierra who really shines as they toss the lead back and forth. She is one of those very smooth, understated, terrifically fluid flatpick guitarists, handling the tune with no fireworks but a laid-back professionalism. You will see her on bluegrass stages for years, believe me. She is one fine picker, making the near-impossible (for most people) look easy. Very offhand, startlingly good. Great listen. Bob