After sitting out the disco years, Dionne Warwick is once again riding the high end of her seesaw career and, judging from her concert at Wolf Trap last night, she isn't about to change directions.

It was obvious that disco could never accomodate a singer as talented as Warwick. For one thing, she is too distinctive a vocalist to blend in anonymously with a percussive mix of strings and horns; for another, her love affair with certain lyrics (and lyricists) run contrary to disco's overriding concern with rhythm and motion.

Although Warwick may have set a record by compressing 23 songs and 13 years into a seven-minute medley, she t reated the majority of songs she performed with exquisite care and control. On "You Needed Me," "Masquerade" and particularly on "Alfie," she proved that her voice has only grown more flexible and powerful with time.

Few comedians can go as long as Mike Neun without occasionally resorting to off-color material when other jokes fail. Neun not only refrained from using them last night; he didn't need them. His songs about Einstein's rumpled wardrobe, amateur-rank espionage and the joys of dancing with two left feet were consistently clever and refreshing.