About 10 years ago, I wrote a piece suggesting that André Previn was Numero Uno in the world of music. Why did I make such a suggestion? Mr. Previn’s versatility, mainly — combined with his excellence.

As you know, he is a pianist, a conductor, and a composer. It’s very important, in my opinion, to compose, if you want to call yourself a complete musician.

In the course of his life, Mr. Previn has had a finger in just about every musical pie. His compositions run the gamut, and so do his performances. One of his sidelines is jazz — and he has just put out a new album: “Alone: Ballads for Solo Piano” (on the EmArcy label).

Promoting the album, Mr. Previn’s PR people remind us of some details. And, remember: It ain’t braggin’ if it’s true.

In 1958, Mr. Previn was Downbeat magazine’s “Musician of the Year.” Six years later, he recorded the first jazz album that ever went gold. Did you happen to own it, or did your parents? It was arrangements of “My Fair Lady.”

Mr. Previn also did a jazz treatment of “West Side Story” — that album won a Grammy. He also treated Harold Arlen — winning another Grammy.

He jazzed up his own music, too — for instance, the score to “Gigi” (which won an Oscar).

The man’s accomplishments, even aside from his four Oscars and shelfful of Grammys, are almost unseemly. To make matters worse (so to speak), he is a superb — simply a superb — writer (of prose, I mean). You can see this in his memoir of Hollywood, “No Minor Chords.”

Before this new release, his previous jazz album was 2001’s “Live at the Jazz Standard,” recorded right here in New York, on East 27th Street (By the way, if you go to the adjoining Blue Smoke to eat, be sure not to skip dessert.) That is a marvelous album, ever listenable.

And the title of the brand-new album is interesting. Why “Alone”? Well, for one thing, Mr. Previn is at the keyboard by himself, with no ensemble. For another — and here I am interpreting freely — he finds himself unmarried, after five wives. And for another: He is alone, in a way, in the field of music (given that daunting versatility).

The first of the 12 songs on “Alone” is “Angel Eyes.” And the playing is typical of Mr. Previn’s jazz: gentle, suave, urbane — songful, too. This is nighttime jazz (but is there any other kind?). And it is somewhat autumnal, elegiac.

It is also exceptionally beautiful. And Mr. Previn’s playing on this album at large is beautiful. I have not heard him play better in years.

He does a number called “André’s Blues” (made up on the spot, apparently). But it doesn’t sound very bluesy — instead, it is saucy and insouciant. He soon plays around with “Night and Day,” making it quasi-Impressionist.

Usually, he does not stray very far from the tune, while improvising. We can hear this in “Bewitched, Bothered, and Bewildered,” among other cuts. Personally, I like an improvisation in which the original is recognizable — there is a maturity in that.

“My Ship,” that wonderful Kurt Weill song, is caressing and dear. And “I Didn’t Know What Time It Was” (Rodgers) is rich and, somehow, deep. Plus, André does some seriously funky — and skillful — things with rhythm.

Incidentally, one of my favorite crossover cuts of all time is Kiri Te Kanawa’s singing of this song (with Nelson Riddle). The great Mark Steyn, however, disagrees with me — majorly. It is one of our few points of divergence.

Mr. Previn plays another Rodgers song, “It Might As Well Be Spring.” In these hands, it is delicate and nimble, fresh and springlike — Previn-like, too. And the artist ends his disc with probably his best-known song, “You’re Gonna Hear from Me” (introduced by Natalie Wood in a movie called “Inside Daisy Clover”).

In general, this album is smooth, refined, knowing — and, as I said, very mature. What’s more, Mr. Previn can’t help being musical. He’s as musical with a popular ditty as he is with Elgar’s Symphony in A flat (of which he is the supreme interpreter).

The disc is determinedly mellow, and if you want sparks, it will not be for you. But all should like it, especially in certain moods, because it goes down very, very easy. (I don’t say, however, that there is a trace of elevator in it.)

And, again, Mr. Previn’s talent is almost unseemly. He refers to his jazz excursions as “once a year for a day.” Apparently, he simply sat down and recorded these numbers, with no “Take Two,” no anything.

He is such a cool cat, André Previn. Recently, I saw a photo of him, sitting at the piano, probably 18 (the age at which he recorded his first jazz album). Slick black hair, cig hanging from mouth. His expression seems to say, “I can do anything.” And, at almost 80, he still can.