They sound like an insect, have six arms and sing like a choir of angels. But Maggie, Terre and Suzzy Roche are really a sibling trio from Park Ridge, N.J. who surfaced in the folk clubs of New York's Greenwich Village around 1977, This is their third album since then, and it bubbles with quirky charm. They harmonize as only blood relatives can, weaving a rich, comforting aural blanket with brightly colored vocal tones. Their uncommon talents are exhibited in full array on a glorious straight rendition of The Hallelujah Chorus from Handel's Messiah. There are six Roche originals plus Steady With the Maestro by fellow folkie George Gerdes and On the Road to Fairfax County by David Massengill. If the acoustic instrumental arrangements are fairly traditional, the song sentiments are more off-the-wall. Take this lyrical couplet: "You work too hard to take this abuse/ Be on guard, jerks on the loose." While the Roches seem on occasion to work overtime to produce unromantic romance songs, "keep on doing" is, in fact, not bad advice for them.