For the final weekend of the 18th annual Pittsburgh New Works Festival, the tasting menu serves up a trio of trios.

I call it a tasting menu because you wouldn't exactly call them plays. It takes a lot of skill to pack a real play into a short form (oddly enough, all three of these run exactly 30 minutes), and the Festival???s developing playwrights are more likely to create character sketches, comic skits or dramatic scenes.

As to the idea of trios, each of this week's three plays coincidentally features three characters, as if exploring the basic ancient Greek discovery that a third actor fruitfully complicates conflict.

The most fun of the three is Robert Isenberg's "Air" (directed by Leah Klocko for Cup-a-Jo Productions), unsurprisingly so, because Isenberg is known locally as a humorous writer (and performer, although he doesn't perform here). It starts dourly, as Ross (Shawn Smith) arrives in a hotel room in Capri determined to commit suicide over a failed romance. But in bursts childhood friend, Lindsey (lively, cute Laura Wagner), who is also in relationship recovery, along with friend Claire (the extraordinary, comically capacious Heather Gray), and the mood shifts to amatory farce.

Most like a play is Alex Goldberg's "The Third Date" (directed by Joseph A. Roots for Rage of the Stage Players). Bradley (a mugging Pete Fernbaugh) is preparing for a date with Angela (Bethany Vahabzadeh), but in walks his dead father (the humorous, eccentric Thomas David Sterner), an obstreperous character who nonetheless plans to do his son some good. The surprises offset any cloying sentimentality.

The third piece, Margaret McCloskey's "Old Head" (directed by Naomi Grodin for Open Stage), is set in Ireland and features literate speeches by a lonely small town librarian (Vince Ventura), who makes much of a visiting American (Tara Lynn Zynel), who is tied to a disturbed husband (Jody O'Donnell). Unfortunately, she has to tell us a lot of things the playwright doesn't have time to show us, and the drama suffers. This feels like an outline for a longer play.

I like the character of the librarian, though. In fact, eccentric and vivid characters are the chief appeal of the festival's final week: the librarian, lively dead father and larger-than-life friend in Capri.

Now, on to the New Works award gala, Oct. 4.

At Open Stage, 2835 Smallman St., Strip; today 5 and 8 p.m.; tomorrow 4 and 7 p.m.; 412-394-3353 or www.pittsburghnewworks.org.