Mose Allison is a puzzle. How could anyone with his flat, monotone voice have commanded such a loyal following over the last 20 years?

The answer probably lies in his superb delivery of lyrics, his excellent piano work and the earthy sociological messages in much of his music.

The evidence showed in his opening Thursday night at the Showboat Lounge in silver Spring. Beginning the first set with a definite instrumental piece, notable for its sprawling melodies, he quickly slid into his blues side, singing the almost nursery rhyme-like "Now You See It, Now You Don't."

Allison has an enthralling way of transforming a melody. He did it last night with Jimmy Rodgers' "You Are My Sunshine." Starting in dirge-like fashion, with only piano and bass accompaniment, he took the song's familiar melody and sentimental lyrics and made them over into a tough voicing of love and hope. He etched each word, each note, into a finely honed groove, holding listeners on the edge of their seats.

Like many who sing the blues, Allison likes to spice his program with the everlastingly topical - the everyday struggle of average people. In his repertoire, songs like "How Much Truth Can This World Stand?" ring out with fervent, iving sociology.

Allison, 49, whose roots lay in Mississippi Delta blues and the complexities of modern jazz piano, sings a buoyant song in which he says he lives the life he loves and loves the life he lives. Let's hope he continues. The Allison trio (including drummer Stan Gage and basist Rick Kilburn) closes Sunday.