The Yonder Mountain String Band would rather blur than straddle any distinctions between the filigreed technical prowess of bluegrass and momentum-generating swirl of jam-band workouts. Given a nice, mid-career bump by the success of the Coen Brothers “Oh Brother” soundtrack, the quartet is currently touring behind their forthcoming new disc, “The Show,” which contains rock tinges such as producer Tom Rothrock (Foo Fighters) and drummer Pete Thomas (Elvis Costello’s Attractions), but neither will invade live renditions of those new tunes out at the zoo this Saturday. Instead, the group will roll and tumble into their scintillating braid of guitar-banjo-bass-mandolin strings on romps such as “Out of the Blue,” and older favorites fans have already heard on the group’s five previous live discs.

Here is the group’s myspace page, featuring three tunes off the new disc. Here they are covering Todd Snider’s “Side Show Blues.”

Singer-songwriter Tracy Chapman is also touring behind a forthcoming new record, “Where You Live.” A harsh and mostly accurate assessment of Tracy Chapman’s career thus far would be that she hit his first disc out of the park and has been diligently trying to duplicate that mixture of plainspoken lyricism and socio-political electricity ever since. Advance word on the new project is that it has loose-hewn, spontaneous feel while featuring such unlikely guests as Flea from the Red Hot Chili Peppers.

In concert, Chapman should generally be given credit for not trying to fix something that isn’t broken: It would disheartening to watch her glitz up or do some politically correct makeover with reggae (the occasional Marley cover nothwithstanding) or afro-pop. Instead her latest, expect heartfelt singing and strumming with a decidedly political bent. “Fast Car” and “Give Me A Reason” are often on the set list. Clips of those modern classics are here and here.

And then there’s Cracker, whose perversely daft sensibility occasionally buttresses and occasionally besmirches the group’s winsome blend of chugging blues-rock and country-inflected pop. Born out of the quirky indie band Camper Van Beethoven, Cracker is fronted by the duo of David Lowery and (less prominently) Johnny Hickman. Alt-rock fans shrouded by the shadow of middle age will shudder to realize that “Teen Angst” is nearly 20 years old, and recognizable Cracker hits like “Low” and “I Hate My Generation” aren’t far behind.

But the group itself offers an example of retaining one’s (frequently juvenile) sense of humor while emphasizing virtues and making minor accommodations to age. This year’s “Sunrise In The Land of Milk and Honey” leads off with a track full of penile double entendres, followed by a tune entitled “Show Me How This Thing Works” that’s similarly carefree, but neither derail the engaging musical chassis comprised of time-tested alt-rock riffs and melodies.

For all you folks fearing 40, here is an anachronistic MTV video of my favorite Cracker tune, “Get Off This,” from “Kerosene Hat.” More recently, here is a live clip of “Euro-Trash Girl” from earlier this year.

Yonder Mountain String Band at the Weesner Amphitheater of the Minnesota Zoo, Saturday, Aug. 15, 7:30 p.m.; tickets $27.

Tracy Chapman at the O’Shaughnessy Auditorium on the campus of St. Catharine’s, Saturday, Aug. 15, 8 p.m. $37.50-$47.50.

Cracker at First Avenue, Saturday, Aug. 15,  7 p.m., $13 in advance, $15 at the door.