I found a pretty cool article on the origins of Old Crow Medicine Show.
Here is an excerpt which references their old timey sound, relative to other styles...
In fact "old-time" music is so called because it predates the recording industry that named it. To the modern ear, old-rime sounds a little like sped-up, drunken children's songs-it plunks and scurries and trips. It's a little dirty, clumsy. It falls apart just enough. If bluegrass is a sturdy, groomed horse, old-time is a mule. (New hot country would be a painted carousel pony.) It's akin to punk rock; it has the same sophisticated lack of refinement, the same defiant authenticity.
You can read the rest of the article here.