When Ray Charles came to Baltimore in June, he had a new, unrehearsed band, and the result was an embarrassing musical fiasco. Last night the same band came to Wolf Trap with three months of road work under its belt and provided the rock-solid support Charles needs to launch his inspired flights of improvisation. The result was a triumphant concert that revealed the sources of Van Morrison's similar show four days earlier.

Charles has lost a little off the top and bottom of his once-sumptuous vocal tone, but his instinctive grasp of phrasing and dynamics was as marvelous as ever. He has sung Hoagy Carmichael's "Georgia on My Mind" more than 200 times a year since 1960, but last night he took off on an improvised coda that made the song brand-new. Pushing the tempo or lagging behind it, singing in a husky whisper or percussive shouts, he found new ways to connect with the homesick, heartsick center of the song. He sang country tunes like "Busted," blues like "Mississippi Mud," standards like "Just for a Thrill" and his old hits like "Hit the Road, Jack," and found ways to recast them all in his gospel-soul style and make them sound fresh.

By contrast, Ruth Brown's opening set was disappointing. Even at age 62, Miss Rhythm has a strong voice, but she devoted most of her set to well-worn arrangements of lounge standards rather than the rhythm and blues with which she made her reputation. When she did tackle her hits from the '50s, she delivered them with the show biz artifice of a recent Broadway show instead of the urgent passion of the original singles. One could make excuses based on her age, but her old label-mate at Atlantic Records, the 59-year-old Charles, had no trouble sounding as bluesy and funky as ever.