Guitarist Pat Metheny has had his current quintet together for three summers now, and that stability paid off in a remarkable display of rapport and versatility at Wolf Trap Sunday night. Metheny, who the day before had been the sole jazz representative at the Live Aid concert in Philadelphia, is one of the few electric fusion artists to strike a happy balance among inventive improvisaton, rhythmic aggression, stretched harmonies and melodic hooks.

Along with King Crimson's Robert Fripp and Adrian Belew, Metheny must be considered one of the trailblazers on synthesized guitar. Last night he used his synth-guitar as a sustained note instrument that could shift tones and shade notes like an operatic voice. At times it soared like a church organ; at others it sputtered with rock noise effects. With Metheny's longtime collaborator Lyle Mays spinning inside a horseshoe of keyboards, the synthesized sounds were layered with a lush density that was always harmonically fresh.

The band's most quickly maturing member is 25-year-old Argentinean Pedro Aznar, who has integrated vocals into fusion jazz better than anyone before him. Forsaking the usual consonant scatting of most jazz singers, Aznar sang wordless vowels that functioned like a most expressive sustained note instrument, often blending wth Metheny's synth-guitar on duets.

Less successful in their use of vocals was the guest group Perri, a pop-gospel quartet of California sisters, who collaborated with Metheny's quintet. Both their lyrics and their vocal arrangements diminished two Metheny instrumentals, "Airstream" and "Jaco," with pop-soul cliches.