I met the Benitez sisters at Palo Alto World Music Month, directly after hearing Ledisi at Stern Grove, where Cecilia Pena Govea and her father Miguel Govea were the opening act.
That they had a jaw’s ass (oops: jaw of an ass) naturally led to a discussion of John McCrea and Vince Difiore of Sacramento’s Cake (who feature vibraslap, and in fact i sat in on such in 1995;
Trumpet: Joseph RamirezVihuela, vocals: Tanya BenítezViolin vocals: Sharon BenítezPercussion: Rodrigo Serna LópezGuitarron, guitar, editing: Carlos Barba
Months later, and after barely making it back over the summit from Mary and Jaimee at Don Quixote, here is their version of “Mexico” (I think it has a weird Charles Ives quality):
Plastic Alto with Mark Weiss 
“That they had a jaw’s ass”
What’s a jaw’s ass?
It’s like a Jew’s Arse but more cake-like, a little less cowbell, slappyhappy vibe. You part the Walter, a little less Cronkitey. What’s a hen weigh? (ED)