The Blackbyrds, the Howard University-based band that appeared at the Cellar Door last night, has had its share of ups and downs. Among the ups was the 1974 Grammy nominee "Walkin' In Rhythm." More recently, the downs have included a lengthy court battle that prevented the band from performing or recording and ultimately severed the group's relationship with its founder and mentor, jazz trumpeter Donald Byrd.

Now things are looking up again. The biggest problem the group encountered last night was getting all 11 members of the band and their equipment onto a stage built to accommodate a group half its size. Once in place, though, the Blackbyrds consistently delivered a tight, energetic and surprisingly refreshing brand of rhythm 'n' blues.

The group now includes two keyboards providing contrasting colors, a fiercely percussive rhythm unit and a strutting, flamboyant horn section that was responsible for most of the fireworks. All told, the inevitable and lofty comparisons with Earth Wind & Fire don't seem as farfetched as some might think.

Chris Thomas, the young Washington impressionist who opened the show, displayed a keen ear for voices and sound effects, even though some of his routines seemed only partially developed. The Blackbyrds and Thomas appear again tonight.