It wasn't conventional, but it did entertain

In the wake of his newly released

Highway Rider

, an ambitious album that includes a chamber orchestra and two drummers, pianist Brad Mehldau turned up in a duo with saxophonist Joshua Redman during a sold-out concert Thursday at Longwood Gardens in Kennett Square.

Their music provided a snapshot of jazz in the 21st century. It was adventurous, sometimes unstructured, and highlighted an unusual repertoire.

How unusual? The 10-song set presented Stone Temple Pilots' "Interstate Love Song" and Nirvana's "Lithium" alongside bop tunes by Charlie Parker and Sonny Rollins. The performances lived up to the weird program by going against the grain.

The jazz tunes didn't swing terribly hard. And the rock songs didn't rock at all.

But the nearly two-hour concert did what jazz is supposed to do - create vibrant music out of familiar songs. Parker and Rollins followed this formula as well.

Mehldau introduced "Interstate Love Song" at a ballad tempo, and Redman's tenor sax displayed an attractive vibrato. Forget rock-and-roll - the reading was more like a recital, the rough edges sanded down to a smooth veneer.

Parker's "Cheryl," a bouncy blues line, began conventionally. But Redman and Mehldau attacked the tune collectively, mimicking each other's licks, rather than as soloist and accompanist. The program also included the songbook standard "My Old Flame" and some less radically performed original compositions.

Without a bassist or drummer, Mehldau carried a heavy load. But the pianist possesses rare stamina, having recorded a series of trio albums whose songs sometimes clock in at a dozen minutes or more. Mehldau alternated between linear on-the-beat lines and intricate counterpoint.

Longwood Gardens provided an exotic backdrop for the jazz-meets-grunge program. One of the premier botanical gardens, its ambience is better suited to a string quartet, but since inaugurating the Jazz Club series in 2008, the presenters have booked an impressive, if limited, number of jazz artists at the Ballroom, a roughly 300-seat venue built in 1929 to house a large pipe organ.

The series' 2010 edition included Terence Blanchard and Jane Monheit; the latter also sold out.