The boundaries of free-form jazz improvisation and jam-based rock have become increasingly difficult to define. While the resurgence of nontraditional song structures has been welcomed by many in the Sacramento Valley, the area is short on bands that can deliver on both fronts. Enter Duntch, a four-piece ensemble that blurs its musical influences with great effect. A listen to the two tracks available at www.myspace.com/duntch, “What This Old Thing” and “Pineapple Seizure,” inevitably will draw comparisons to Skerik, any Charlie Hunter ensemble, or Medeski Martin and Wood’s finer jams. Duntch plays Luna’s Café, located at 1414 16th Street, on Saturday at 8 p.m. with Delayed Sleep and Instagon. The cover is $6, and all ages are welcome. While you’re at it, sample some of the great food at one of Sacramento’s most intimate venues.