I played Matty Groves for a circle of bluegrass pickers one night. The reason was, many of them were familiar with Shady Grove but not Matty. I contend that Matty Groves is the ancestral version. Anyway, I sang the thing in its entirety, with little room for picking breaks (which are the be-all for lots of bluegrassers), and nobody fell asleep. In fact, the story in the song is interesting enough with the sex and violence that I seemed to have everybody's attention. But I'm pretty sure they would balk at a more frequent repetition of it. Timing, I believe, is the key factor in these long ballads.