It isn’t quite a tune or even a riff: It’s just a short run of about six or seven repeated notes. It almost sounds more like a hip car alarm than a song. Sometimes the figure is played by one of the three front-liners – the pianist, composer, and bandleader Andrew Hill, the trumpeter Charles Tolliver, and the tenor saxophonist Greg Tardy – alone, sometimes in conjunction with one or both of the other two. When they play together, in any combination, the notes are not in unison, but come staggering after each other with a built-in delay, suggesting an echo in a dark cave.

This is the title track of Mr. Hill’s new album, “Time Lines” (Blue Note 35170), and maybe we should take that name seriously. Perhaps this isn’t a melodic line so much as a time line, and it often feels like a time-travel sequence in a science fiction movie, like moving forward and backward between past, present, and future.

Mr. Hill also opened his four-night run at Birdland with “Time Lines,” which commemorates 50 years since his first album (“So in Love,” recorded in his native Chicago in 1956). The late Alfred Lion, the founder and major impresario of Blue Note Records, once said he regarded Mr. Hill as one of his most important “discoveries” – fully on a par with Thelonious Monk. All of Mr. Hill’s dozen-plus albums for Blue Note in the 1960s were outstanding, and his fourth, the 1964 “Point of Departure” (featuring Eric Dolphy, Kenny Dorham, and Joe Henderson), was an all-time classic: one of the quintessential statements of a great jazz era.

At that point, free jazz (or avantgarde) was regarded by many, even those who liked it, as the end of the music’s evolution: a stop sign, beyond which one could go no further. Mr. Hill was one of the few to show that the elements of free jazz could be utilized much like the components of swing and bop, and he created a music that was equally informed by the free movement and by the hard bop that surrounded him at Blue Note. Yet over the last 40 years, what at first seemed like a deliberate (and very successful) attempt to bring two styles together now seems perfectly natural, the highly personal language of one singular composer-bandleader-pianist.

Mr. Hill returned to Blue Note at the height of the neo-bop era in the late 1980s for a pair of albums, and more recently he has recorded several first-rate projects for the independent Palmetto label (including the fine “Dusk”). “Time Lines,” recorded last summer, marks the start of his third tenure with Blue Note. Even though the album has just been released, it’s clearly a critical hit, and on the strength of it, Playboy magazine has already proclaimed Mr. Hill “Jazz Artist of the Year 2006”; editor Christopher Napolitano presented him with a plaque to that effect shortly before his first set at Birdland.

Interestingly, I’m not sure if I would rank “Time Lines,” fine as it is, as one of Mr. Hill’s all-time greatest albums – I don’t think I will listen to it as much in the future as I do “Dusk” or “Passing Ships” (the 1969 session finally released three years ago, to universal acclaim). Much of the “Time Lines” music worked better on the record than in person. Mr. Hill seems to have set himself the challenge of sustaining listener interest without a lot of tempo variation: nearly every thing on the album is slow and tranquil. Messrs. Tolliver and Tardy allow themselves to get louder and softer as the occasion demands, even if they don’t employ such standard attentiongrabbing devices as double-timing. Whenever the drummer, Eric McPherson, has the spotlight to himself, he seems intent on playing the world’s slowest and softest drum solo – as if to prove that drum solos aren’t necessarily always loud and fast.

Normally Mr. Hill’s music is much richer in a conventional melodic sense, but here he shapes the playing of the ensemble in what seems like a more spontaneous way, and the effect is more hypnotic than tuneful. He has done much of his best writing for ensembles of six or seven pieces or more; here he lets his two horns take their own sweet time in a wide and open harmonic space. Mr. Tardy, who has played mostly tenor at Birdland, plays mostly bass clarinet on the album and displays a very distinct tone and personalized timbre.

He can make both horns almost sound like some bizarre Middle Eastern double-reed instrument. Mr. Tolliver, contrastingly, plays this idiosyncratic and demanding music with a straight-up tone, achieving individuality without the use of any kind of distortion.

While the Birdland set began with a longish reading of “Time Lines,” the album begins and ends with two versions of “Malachi” (by the ensemble and as a piano solo). By Mr. Hill’s standards, it’s a sweet, almost sentimental tune, which he has dedicated to the late Malachi Favors, the bassist in his first trio (and on his first album), who later became famous with The Art Ensemble of Chicago. This is as close as Mr. Hill comes to nostalgia, but it’s just another trip on the time line.

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Speaking of time lines, I have never seen such a point spread as the one among the ages of the divas opening in New York this week, beginning with Kitty Carlisle Hart (95 years young, God bless her), the grand dame of the American musical theater (not to mention movies, opera, and television), in a rare week at Feinstein’s, to Barbara Cook, one of the great living interpreters of the American songbook, opening a run at the Cafe Carlyle (more about her soon). Yet if you took Ms. Cook’s age (77) and subtracted it from Ms. Hart’s age, you would get something fairly close to the age of Samantha Sidley, the college-age prodigy who has just won the first annual Oak Room Young Artist Competition (of which I was a judge). Ms. Sidley could easily be Ms. Hart’s great-granddaughter: Both have an irrepressible twinkle in their eye that fully knows a diva’s first job isn’t necessarily even singing but charming a crowd with whatever you’ve got going for you – and in the case of all three ladies this week, that’s something considerable.

Until March 4 (315 W. 44th Street, between Eighth and Ninth Avenues, 212-581-3080).