Curtis & Loretta are as good an argument as any for the preservation of a space within the current acoustic scene for, you know, folk music. Not that there's anything wrong with coffeehouse singer-handwringers or collegiate rockers with mandolins. And not that space shouldn't also be made for Indonesian gamelans, Nordic roots, or anything else. It's just that the perfect, ringing Celtic harmonies of Loretta Simonet and Curtis Teague represent one of the purest and most accessible pleasures in local music. And the duo's latest album, Sit Down Beside Me (Haymarket Music), provides a perfect showcase for the lyricism that a longtime couple can discover with vintage traditional instruments (Teague on mandocello, Simonet on Celtic harp). Forgoing the duo's fine originals, Sit Down is a collection of traditional songs from the British Isles, sung with confidence and feeling. The tunes are restorations as surely as the vintage instruments upon which they're played, but if subjects such as whales or heartbroken maidens don't particularly speak to you, the voices recalling them will.