Though a major around the British Commonwealth, the Caribbean-born and English-raised Joan Armatrading remains a minor cult figure here. That may change if she can give more American performances like the one she gave Saturday night at the Carter Barron Amphitheatre. Backed by an excellent rock 'n' roll quintet, Armatrading filled her quirky compositions with an immediate personal style.

One barrier to Armatrading's popularity here has been her refusal to fit into any accepted category. Although she had a definite West Indies accent in both her voice and music Saturday, there were also streaks of American rhythmn 'n' blues, confessional folk songs, English rock 'n' roll and bluesy cabaret jazz.

As great singers like Billie Holliday and Van Morrison had before. Armatrading transformed any style into a dramatic vocal exercise.

Her lyrics were unexpectional tales of romance, but like Holliday and Morrison, Armatrading delivered all the emotions hinted at in the words. She would pause in midline to build expectations, then finish the line in a sudden upward spurt of syllables. A sore throat got the best of her at the end, but for most of the night she sang with a deepthroated warmth at every pitch and tempo.

In the opening act, Michael Katakis performed alone on acoustic guitar and piano. His songs werecatchy but basically sentimental in the style of Dan Fogelberg or John Denver. Katakis' commercial future is considerably brighter than his artistic future.