And yet, among the 72 keyboard artists selected by Philips Classics for the landmark “Great Pianists of the 20th Century” series, Mr. Kovacevich is the only American with an active career to be celebrated with not one but two volumes of recorded work. Since the 1960’s, he’s produced one admired album after another on two major labels, Philips and EMI, including an exceptionally vital account of all 32 Beethoven piano sonatas, which EMI released in 2003. Even so, when Mr. Kovacevich made a rare New York appearance recently at the Metropolitan Museum of Art, the audience numbered no more than a few hundred people.

The small turnout is easily explained. The Met is currently presenting a fascinating run of recitals by distinguished, relatively unfamiliar pianists—but as far as I can see, the series has gone almost entirely unpublicized. (I’m eager to hear the next two artists: the superb French pianist Mark Laforet on Feb. 2, and the Irish Beethoven specialist John O’Conor on Feb. 23.) It’s a sign of how little pizzazz the museum puts into its concert and lecture program that one must approach the auditorium through a deserted cafeteria with upturned chairs on the tables. Moreover, the program notes contain not a shred of biographical information about the performer. They don’t treat Van Gogh that way.

Another factor is that Mr. Kovacevich, who was born in San Pedro, Calif., in 1940, became an expatriate at the age of 19, when he went to England to study with the legendary British pianist Myra Hess. London, where he’s revered, has been his home ever since. New York concertgoers are provincial about favorite artists: If you don’t turn up with some regularity or have a massive publicity machine behind you, you’re nobody.

And then there was something oddly ill-defined about Mr. Kovacevich himself. Reports circulated that he suffered from more than the usual performance anxiety. Whenever I heard mention of him, it was most often along the lines of “Wasn’t he once married to Martha Argerich?” (He was indeed the third husband of the most charismatic woman pianist of our time.) Or: “Didn’t he used to be Stephen Bishop?” Well, that was his first professional moniker—the surname was that of his stepfather. Some years later, he added his own name and became Stephen Bishop-Kovacevich. And then, about 10 years ago, he simplified that mouthful to Stephen Kovacevich. Equivocating about your name is not a good career move.

In the album notes to Mr. Kovacevich’s complete set of Beethoven sonatas, the EMI producer John Fraser calls the pianist “an artist of almost self-punishing honesty and integrity.” Judging from my first live experience of Mr. Kovacevich’s artistry, a more accurate description would be self-effacing—in the best sense of the word.

Mr. Kovacevich’s program—played with an unruffled focus that got to the emotional and lyrical core of the music—offered an embarrassment of complementary riches. His opening piece, Berg’s Sonata, established that we were in the presence of a pianist whose voice travels easily between introspection and extraversion without false drama. There was no preciousness in this crystal ball of early modernism (or late Romanticism), only a steady illumination of the way in which, as in Proust, musing becomes feeling.

The next piece, the first in a set of four Beethoven Bagatelles from Opus 126, brought to the fore a quality I noted throughout much of the recital—gentleness. I grew up listening to recordings by Dame Myra and hearing stories about how her lunchtime recitals had raised Britain’s morale during World War II with her indomitable poise and purity. Her ghost was present in her protégé’s playing of these exquisitely unfrivolous trifles—one could imagine them lifting the composer’s spirits during his last dark years.

Another quality that Mr. Kovacevich learned from his mentor is a sense of spaciousness. Too often I’ve felt rudely jerked through Beethoven’s multi-chambered Sonata No. 28, Opus 101—the gateway to the futuristic last four sonatas. But in this case, the pianist maintained such clear-eyed purposefulness that the progress from tenderness to sternness, gravitas and jubilant resolution was as easy to follow as Ariadne’s thread. The tempo marking for the opening movement is “ Allegretto, ma non troppo,” which suggested something else about Mr. Kovacevich: For all the heart-filling presence of his playing, he’s an artist of great self-containment, allowing nothing to become “troppo”—too much.

If Beethoven’s Hammerklavier Sonata is the Everest of the piano literature (and Mr. Kovacevich’s scaling of it on disc is a hair-raising tale of triumph over adversity), Schubert’s Sonata in B-Flat Major seems to traverse the whole of early 19th-century Central Europe, illuminated by the embers of the composer’s last days on earth. Mr. Kovacevich devoted the program’s second half to this valedictory masterpiece, and rarely have I been held so rapt by the quality that Schumann noted in the questing music of his beloved predecessor—its “heavenly length.”

Mr. Kovacevich’s mastery of the pedal cast the nearly 40-minute work in a hazy nimbus whose shadows and flashes of light reminded me of the atmosphere in Rembrandt’s The Polish Rider at the Frick. Just as the painter caught the young man’s profound uncertainty about his destination by conveying the sense that he’s moving forward and backward simultaneously, the pianist, with delicate adjustments in pulse and rubato, captured Schubert’s final ride as a journey into timelessness. When it was all over, my companion, a poet who had kept his eyes shut throughout the performance, made a remark that summed up Mr. Kovacevich’s extraordinary playing: “There was nothing between us and the music. It’s as if he wasn’t even there.”

Singers often say how naked they feel standing in front of an audience with nothing to rely on but the condition of their vocal chords. But in certain ways, pianists are more vulnerable. For one thing, they perform facing the keys, not the audience, and are thus unable to woo their listeners with waves of personal charm; their voice is heard only through the workings of a big black box, and a noble profile goes only so far. For another, even more than singers or violinists, pianists must contend with the back-from-the-dead syndrome: the hovering presence of all those ghostly giants whose way with Beethoven or Chopin has assumed the status of "definitive." (A 30-year-old piano buff, speaking of a pianist who has been dead for 41 years, will say, "The Barcarole was very good, but you should have heard Cortot!") And with no other musical partnership is the disparity between player and instrument so pronounced. In contrast to the violin, which is like a natural extension of the body, the piano is an alien, mechanical beast, and the taming of it, as many pianists will testify, can do you serious bodily harm.

Mr. Ohlsson is a pianist who has never met a piano he couldn't tame. If his international career hasn't quite fulfilled the promise he showed after winning the Chopin Competition in 1970, it has been Bunyanesque in its fearlessness. According to the program bio, he has played more than 80 piano concertos everywhere between Hong Kong and Jacksonville. In the second of a wonderfully off-beat series of recitals devoted to Busoni, the most formidable pianist at the turn of the last century and a Janus-like figure who straddled the peaks of Bach and Liszt while envisioning the music of the future, Mr. Ohlsson came close to blowing the man down.

In 1920, an Italian critic wrote that Busoni at the keyboard had "a quality [of tone] that was cold and almost inanimate. From this perfectly even basis he would start and build up a climax that reached the extreme limit of what is possible to a pianist, an avalanche of sound giving the impression of a red flame rising out of marble." Mr. Ohlsson, a big, bearded man of sunny countenance, can make an avalanche of sound as impressive as there is today, but it comes out of genial showmanship, not white marble. His dynamics have three decibel levels: pianissimo, mezzo-piano and fortissimo, with little in between. Showmanship with a smile may be the only way to approach a weirdly glittering program of Busoni's harmony-packed transcriptions of Bach and Liszt organ pieces and a selection of the composer's own short pieces. These included the Sonatina Seconda (1912), which ventures with giddy courage into Arnold Schoenberg swampland, and the Elegy No. 4 (1907), a delightful attempt at Orientalism that employs the distinctly un-Oriental "Greensleeves" as its principal theme. Mr. Ohlsson's homage to the sublimely wacky Busoni ends with a third program on March 23.

Two earlier recitals in Carnegie Hall demonstrated that there are virtuosos in our midst destined to become the ghosts of future generations. The first was the Japanese pianist Mitsuko Uchida, who has launched a two-season series of concerts in Carnegie's "Perspectives" series. Ms. Uchida has an aura that is uniquely hers. A slight, striking woman in flowing silks who is now in her 50's, she projects exoticism, exactitude and earnestness all at once. Having made her name as a peerless interpreter of Mozart, she has recently turned her strobe-lit gaze on the Sch--'s of Vienna, the city of her musical training: Schubert, Schumann and Schoenberg.

The last came first: Schoenberg's Three Piano Pieces (Op. 11), of 1909, in which the father of atonality sought to enlarge his expressive range by severely compressing the flow of musical ideas. These once-radical little works, alternately dreamy and explosive, can still knock listeners off-balance. But Ms. Uchida's forte is to create a kind of hypnotic continuity through the pressure of sheer feeling, and since she's a performer in whom anxiety and serenity seem interdependent, she's the ideal interpreter of this self-consciously moody revolutionary.

Her next piece, Schubert's Sonata in G (D. 894), uses expansion rather than brevity to achieve its effects. Here, because of Ms. Uchida's tendency to approach every phrase as though it were a moment of supreme importance, the beautiful forest sometimes got lost for the beautiful trees. In the second half of the program, which was devoted entirely to Schumann's mighty Fantasy in C (Op. 17), she stretched her embrace to its limits. In this 30-minute work, the emotional range goes beyond the neurotic and the romantic to the titanic. Although Ms. Uchida's grip was inescapable, I was again made aware of her need to italicize every statement, such that the work came off more as a sequence of majestic declamations than as the release of a fantastic, fevered imagination. At a time when music schools are turning out faceless prodigies, her brand of personal pianism is exhilarating. But can there be too much of a good thing?

A week later, I attended a recital that ranks with the half-dozen or so greatest piano performances of my experience, right up there with those of Vladimir Horowitz, Artur Rubinstein, Arturo Benedetti Michelangeli, Maria Tipo, Maurizio Pollini, Radu Lupu and Martha Argerich. The pianist was the 32-year-old Norwegian Leif Ove Andsnes, who has rapidly established himself as perhaps the standard-bearer of his generation. In appearance, Mr. Andsnes is as far from the romantic stereotype of the piano virtuoso as you can imagine: He eschews white tie and tails for a modish black suit and a buttoned-up shirt-no tie. His hair is the crewcut of the nice fellow down the road who might come over to help with a few chores; his manner suggests that he's simply there to do what he does well.

He played an impeccably thought-out, similarly self-effacing program: pieces by his beloved Grieg, Debussy and the Japanese composer Akira Miyoshi sandwiched between two monumental works by Chopin. At every turn, I felt as though the music were speaking through Mr. Andsnes rather than being "told" to us. He's an astonishing interlocutor with a technique that doesn't call attention to itself, but easily supports his finely balanced sense of the work's structure, colors, pulse and prevailing weather. Like Walter Gieseking, one of the old masters whose transparency and pearly elegance he brought to mind, Mr. Andsnes unleashes his full, considerable power only at the most telling moments. And like the greatest pianists, he's not an international product, but an artist who carries with him the culture of his upbringing-in his case, that of a clean, sky-washed, seafaring community off the coast of Norway, where a sense of the larger universe goes hand in hand with quiet, daily industriousness. I felt all this most keenly during his playing of the Largo movement of his closing piece, Chopin's Sonata No. 3 in B minor (Op. 58). Here, there were no giants of the past looking over his shoulder-only a thoughtful young man entirely at one with his piano, playing beautifully to Chopin, to himself and to us.