THEY SAY the neon lights are bright on Broadway. What they don't often say is that the brightest, hottest lights are sometimes shining on other streets. Hence, a handful of original cast recordings from the illuminating new musicals to be found off-, and way-off-, Broadway:

"Falsettoland" (DRG). This musical, composer-lyricist William Finn's most accomplished and emotional, is actually the final chapter in his marvelous "Marvin trilogy," which impressionistically sketches the life and loves of endearingly neurotic Marvin, who leaves his wife and son for a male lover -- then loses him, too. But Marvin valiantly tries to keep his unconventional family together, and as "Falsettoland" unfolds, his son Jason's impending bar mitzvah brings about a taut truce with ex-wife Trina, and a reunion with his ex-lover Whizzer.

Marvin's happiness is shadowed by the appearance of a mysterious new illness -- this is 1981. Guiding us expertly from laughter to tears, Finn explores the nature of the contemporary family, love and death, and provides perhaps the truest stage picture to date of how AIDS affects us all. Once regarded as a Sondheim wanna-be, Finn has grown into his own distinctive style, and his score, which features such riotously comic set pieces as "The Baseball Game," and heart-shredding ballads like "What Would I Do?" is beautifully sung by an ensemble cast headed by Michael Rupert as Marvin.

"Once on This Island" (RCA Victor). For those of us who can't afford a ticket to the islands (even the island of Manhattan) this dark, cold, recessionary winter, the cast recording of "Once on This Island" might serve as a relatively affordable escape. It's a small jewel of a musical, sparkling in Caribbean Carnival colors, a folk tale told in bright rhythms and exuberant singing.

Lyricist Lynn Ahrens and composer Stephen Flaherty, who created the underrated musical farce "Lucky Stiff," adapted Trinidadian author Rosa Guy's novel "My Love, My Love," which unfolds as a group of Caribbean peasants huddle together to wait out a tropical storm. The album begins with a startling thunderclap, a young girl cries out in fear, and to soothe her, the ensemble performs the legend of Ti Moune, who leaves her village in search of her lover, sent by the gods of her island to test the strength of her love.

"Once on This Island" provides a lesson on the persistent power of myth in our lives, but more immediately, plenty of much-needed warmth and color.

"Forever Plaid" (RCA Victor). A novelty musical in the vein of "Beehive," this is a parody/celebration of the flip side of the '50s, a funny valentine to the male harmony groups of the '50s: the Hi-Los, the Four Preps, the Crew Cuts . . . . The antithesis of the rebel greasers and surfers and bikers of the era, these clean-cut, bow-tied, polite-to-parents Nice Guys posed no threat, and since their homogenized style never had much in the way of distinctive personality in the first place, it's easy to evoke the whole bunch in one group.

Meet the Forever Plaids, a four-guy harmony group. While en route to their first big gig (at the Airport Hilton Cocktail Bar), they were sideswiped by a school bus and went where all teen angels go. But once in heaven, Sparky, Jinx, Smudgy and Frankie (where they are members of the Glee Club, natch) are allowed back to make the record they never made. "Forever Plaid" winks at the defiant squareness of the sound, but has real affection for the genre, too. So the cast album makes a fine souvenir of the show (there's even an autographed wallet photo) and stands as a record on its own (you might have ordered it from a late-night TV commercial) with creamy harmonizing on lovingly recreated versions of "Three Coins in the Fountain," "Perfidia," and Johnny Ray's tear-stained "Cry," that manage to be simultaneously earnest and tongue-in-cheek. "Forever Plaid" will be presented at Ford's Theatre beginning March 17.

"Mama I Want to Sing Part II" (Reach). The gospel musical about the Troy family became the longest-running black musical in theater history -- after eight years, it's still playing at the Hecksher Theatre in New York -- so it was only a matter of time before it inspired a sequel.

This one is less bio and more soapy love story, and peppers the powerfully sung gospel/pop score with R&B/rap rhythms, but it again features singer/actress D'Atra Hicks, whose spiraling, stratospheric sound could embarrass an ambulance siren in a showdown. Doris Troy, the Harlem gospel chorister turned pop singer ("Just One Look") whose life was the basis for the first musical, plays her own "Mama."

"A Funny Thing Happened on the Way to the Shoreham" (Foggy Bottom). A five-year run at the Shoreham Hotel's Marquee Lounge is some kind of record. And now there's a record of Washington singer-satirist Joan Cushing's record-setting revue. Two records, actually. Cushing's self-produced double-LP features 30 samplings of vintage Mrs. Foggybottom & Friends, including such clever favorites as "I'm in Heaven at Hechingers," (about the hardware store as singles-bar) and the "Water Music Minuet" (about the drug-testing frenzy of the late Reagan era).

At the center of each side is a one of Cushing's tart, dry-as-a- perfect martini monologues in the guise of Ultimate Socialite Mrs. Foggybottom, who, from her eighth-floor Watergate apartment can see "absolutely everything that's going on at the White House, darling." The sound quality occasionally leaves something to be desired, and the audience response is suspiciously boisterous now and then, but the performances by Cushing and her cast of local lights are spirited. So "A Funny Thing" makes a fine time capsule of what really went on in Washington in the '80s.