MUSIC REVIEW : Chemistry Lesson : Style: The jazz group Fourplay combines four musicians and lets them cook, to the audience’s delight.

Former San Diegan Nathan East played a triumphant homecoming last Friday night as the new all-star group Fourplay concluded its debut tour at the Spreckels Theatre in downtown San Diego.

With friends and family in the audience, East shined as the charismatic centerpiece of the group, an assemblage of stellar musicians that clicks incredibly well. East gave his six-string electric bass the most rigorous of workouts and even turned in a soulful, falsetto vocal on the group’s encore, Marvin Gaye’s “After the Dance.”

Playing to a crowd of 1,250 in the 1,350-seat theater, following a loud but musically uninspiring opening set by saxophonist Warren Hill, Fourplay proved that it is light-years beyond its pop-jazz radio peers.

The group quickly established an easy rapport with a lively audience that sang, clapped and snapped fingers along with the music.

Maturity is the key to Fourplay. Keyboard player Bob James, 52, and drummer Harvey Mason, 44, the band’s senior members, can’t match East and guitarist Lee Ritenour in charisma. East and Ritenour danced around the stage as they coaxed line after inventive line from their instruments. But James and Mason exert their own guiding influences on the music through their tasteful, understated playing.

Fourplay has talent to burn and great original material, but the subtle chemistry among its members is what makes the music cook. Here are four humble players who know that the spaces between notes can be just as valuable as the notes themselves.

The group has rapidly gained a wide audience for its accessible but intelligent music. Fourplay’s self-titled debut recording became the longest-running number one title on Billboard’s Contemporary Jazz charts last week, its 27th week on top.

But Fourplay is even better live, with all four members taking long, imaginative solos. The evening’s only downside was a poor sound mix, especially detrimental to Ritenour and James. Some of their best efforts were barely audible and seemed to vanish into the soaring space.

Friday night’s set opened with James’ “Moonjogger” and Ritenour’s “Foreplay,” a pair of gentle numbers that featured James’ dreamy, understated improvisations on acoustic piano.

Next came “101 Eastbound,” written by East with his brother Marcel. East worked his potentially cumbersome, wide-necked electric bass with the ease of a conventional electric guitar. At times, as he improvised bass lines, he scatted along in unison with his voice, sounding like the next George Benson.

Other highlights of the set included “Quadrille,” a Chick Corea-like James composition, delivered without the busy clutter that has marred some of Corea’s more recent group efforts; Ritenour’s “Wish You Were Here,” on which James and East eased in to complete each melodic phrase begun by Ritenour; and Ritenour’s phenomenal solo introduction to his “October Morning,” a song that peaked with a rousing duel between Ritenour and James.

Following a standing ovation for the set-closing “Bali Run,” the upbeat opening track from Fourplay’s new recording, the group returned to spotlight East on “After The Dance.” El DeBarge handled vocals on the recording, but East ably filled in, pulling yet another tool from his deep musical bag.

Fourplay is the best electric jazz band to come along since the first fusion wave of the early-1970s, when groups including Corea’s Return to Forever, Weather Report and Mahavishnu Orchestra fused the driving electricity of rock with the complexity and intelligence of jazz.

The group plans to record again later this year. Given the busy careers of its members outside this group, it may be several months before Fourplay tours again. Then again, maybe the surprising success of their debut release and tour will prompt a more rapid return to the road--if East’s inevitable solo career doesn’t soon lure him away from the group for good.