There’s something about Andy Bey that preconditions you to expect surprises. The veteran singer and pianist never lets you get too close, though there are a few elements you can always count on. For starters, there’s his familiar juxtaposition of the world’s most rapid vibrato and its slowest tempos, and how he gets the two elements to contrast and accentuate each other. Then there’s his focus on lesser-known but surprisingly worthy numbers from the obscure corners of the Great American Songbook, which he intermingles with more widely heard standards, reinterpreted in such an original way that they seem brand new. Lastly, Mr. Bey possesses something that no other contemporary singer (at least doing the Songbook) seems to have: a remarkable multiple-range virtuosity that allows him to sing in different registers.

Mr. Bey, a Newark native, was just 17 when he formed Andy & the Bey Sisters with his siblings, Salome and Geraldine, in 1956, and the trio recorded three well-received albums for RCA and Prestige before splitting. In the intervening three decades, he was scarcely heard from on records, apart from guest vocals with an impressive variety of jazz stars such as Horace Silver and Howard McGhee. When, in 1995, Mr. Bey recorded “Ballads, Blues And Bey,” his first widely heard solo album, many fans who had kept track of him assumed that he was back on the scene, steadily working the mainstream clubs. No such luck: In the 12 years since, he’s only released three albums. But this season, the 68-year-old will release a long-awaited new album (actually recorded 10 years ago) and a valuable re-issue of one of his forgotten gems, “‘Round Midnight.”

In 1965, “‘Round Midnight” marked the last appearance of Andy and the Bey Sisters. The trio was generally described as a combination of jazz and gospel elements, and it would be difficult to imagine a more direct application of those styles; all 10 numbers on this disc (which is part of Fantasy’s ongoing series of reissues remastered by the original engineer — in this case the legendary Rudy Van Gelder) are saturated in both heritages. The three Bey siblings imbue “Hallelujah, I Love Her So” with so much spiritual feeling that they make even Ray Charles seem like a nonbeliever by comparison.

To a certain extent, one expects this to happen with melodies by the great jazz composers, like Ellington’s “Solitude” and Monk’s “‘Round Midnight”; both performers enjoyed a profound relationship with the black church, as well as with the deliberately pious “God Bless the Child.” Yet Andy, Salome, and Geraldine also make Cole Porter and Anthony Newley sound like profoundly religious experiences. They even pull it off with the Hollywood pseudo-folk hit, “Tammy.”

Just as, 20 years earlier, the remarkable Billy Eckstine had captured the big-toned ballad sound of Dexter Gordon and Gene Ammons in the inner timbre of his bass-baritone, Mr. Bey accomplished the same thing in relation to the great saxophonists of his day on his piano; his reading of “Feelin’ Good” sounds directly inspired by John Coltrane’s edition, beginning with an invocation-like intro that sounds like he’s down on his knees, praying.

In recent years, Mr. Bey has extended his legacy of turning up in the least expected places. In 1998, he recorded (on “Shades of Bey”) singer-songwriter Nick Drake’s most famous composition, “River Man,” in an attractive medium-tempo arrangement using guitar and strings. Two years later, Detroit radio station WDET produced an all-star anthology of famous artists performing live that included Mr. Bey doing “River Man,” but considerably slower, backed with only his own piano, and sounding deeper and more moving than he did on the previous recording.

Then earlier this year, the French piano and bass team Guillaume de Chassy and Daniel Yvinec released a fascinating album called “Wonderful World,” which included two guest vocals from Mr. Bey. “It Could Happen to You” is first-rate Bey, but “The Next Time I Love” (from Jerry Herman’s 1960 off-Broadway revue, “Parade”) is even better: Mr. Bey keeps his solo chorus short, simple, and incredibly sweet, and, in a move typical of his career, contributes one of the most moving performances in his entire canon to somebody else’s album.

“It Ain’t Necessarily So: Live at Birdland” is also a typically unexpected move. Who would have thought that Mr. Bey’s first new album since 2003 would be a 10-year-old live tape? Backed by Peter Washington on bass and Kenny Washington on drums (a few years before they became two-thirds of the Bill Charlap Trio), Mr. Bey begins by showing that his gift for switching vocal registers enables him to do a better job of singing Ira Gershwin’s “Porgy and Bess” than most solo vocalists; instead of featuring a call-and-response between soloist and choir, Mr. Bey sings different parts of the song as both a baritone and a tenor (not to mention a singer and a pianist).

My ears linger a bit longer on two exceptionally touching melodies, both written by Broadway-centric composers, but not for specific shows: Mary Rodgers’s “Hey, Love” and Cy Coleman’s “On Second Thought.” Each one takes Mr. Bey nearly 10 minutes to sing, and it’s worth every second.

The title of the first suggests an energetic romp, but Mr. Bey transforms it into one of the slowest and most melancholy tunes in his songbook. Contrastingly, we know from the get-go that “On Second Thought” is going to be a heart-grabbing, Sinatra-style saloon song, and Mr. Bey doesn’t disappoint. Appropriately, for a song about second-guessing oneself and changing one’s mind, Mr. Bey seems to have a different voice for every level of thought. When he rises and falls between belting in baritone near the end (“you wonder what to do”) and then dropping back down to a more contemplative tone, he builds and releases tension in the most direct and effective way.

Mr. Bey also makes “All The Things You Are” — which originally was a quasi-operatic aria— and “Brother, Can You Spare A Dime,” a heavy lament of social significance, into fast and furious swingers. “I Let a Song Go Out of My Heart” finds Mr. Bey switching voices from bass to falsetto (in the tradition of Fats Waller, Dean Martin, and Elvis Presley, who also sang different parts of the same song in constantly shifting registers), and becoming a one-man Bey Sisters.

That tells you a lot about the artistry of Andy Bey. Whenever you think you’ve got him all figured out, you find out that it ain’t necessarily so.

wfriedwald@nysun.com