Good improvisational comedy often has more in common with jazz than it does with stand-up. A troupe of players hops onstage and begins creating whole new realities by piling their imaginations atop a single contribution from the audience. We've all seen that — and we've all seen what happens when it doesn't work. But we said it's the good stuff that's like jazz, notes played within subtle structures, harmonizing and snapping in a syncopation that casual viewers won't even notice. So it is for Babel Fish, which has won five recent Underground Throwdowns at the Westport Coffeehouse. The group often features KC improv veterans Patrick Craft, Joe Henley, Nathan Stewart and Jim Sturgill, who know how to tinker with form just so. It's impossible for improv to be perfect because there's no script. But that's the entire appeal, and Babel Fish always keeps the form interesting — and almost always keeps it hilarious, too.