Last week "10,000 Days," the new album by Tool, sold about 564,000 copies. That was easily enough to put the album on top of the Billboard chart, and it's about twice the sales figure for the new self-titled CD from Pearl Jam, which was released on the same day.

Even so, many nonfans probably had no idea that Tool even had a new album in the shops. After the early 1990's, when MTV seemed to be playing the band's eerie videos nonstop, Tool started shedding casual listeners while retaining — even attracting — serious ones.

No doubt none of them were surprised to discover that "10,000 Days" is full of grand, heavy, slightly mysterious progressive rock. If it takes 11 minutes for a Tool song to reach its writhing, crashing climax — well, that's how long it takes.

Tool's current single, a six-minute marvel called "Vicarious," reached No. 2 on Billboard's modern rock chart, but it isn't the kind of song that might cross over to pop radio. And while other bands are teaching fans the joys of legal downloading, Tool is one of the few current big-name acts that refuse to sell through iTunes. (Others include Kid Rock, Linkin Park and Radiohead.)

So "10,000 Days" (Volcano/Zomba/Sony BMG) is purely a CD, though it's a pretty elaborate one. Along with those 77 minutes of music, you get a wraparound hardcover case; the booklet is printed stereoscopically, with lenses built into the cover. This is the kind of CD that makes a $9.99 download seem like a rip-off.

We have grown used to hearing musicians and listeners pine for the glory days of the vinyl LP. (That warm, crackling sound! Those 288 square inches of blank canvas!) And a generation that came of age in the 1980's has found ways to mourn the demise of the lowly cassette. (Read all about it in the book "Mix Tape: The Art of Cassette Culture," edited by Thurston Moore of Sonic Youth.) Now, listening to Tool's glorious, immersive new album, it's possible to mourn the tragic demise — is there any other kind? — of the CD age. Remember the compact disc, with its finicky packaging, its bloated running time, its charming vulnerability to scratches?

Certainly "10,000 Days" evokes a bygone time when musicians expected listeners to swallow their albums whole (unlike vinyl records, which required constant flipping), and in order (unlike MP3's, which encourage constant flitting). In the CD age musicians learned to add their own diversions — skits, interludes, collaborations — to keep listeners refreshed on a journey that might last nearly 80 minutes. In "10,000 Days," the band's first album since the 2001 masterpiece "Lateralus," labyrinthine songs are cushioned by intros and outros and digressions. (One of these, "Lipan Conjuring," is 71 seconds of chants.) Unlike LP's or MP3's, CD's encourage musicians to take their time.

Tool's lead singer, Maynard James Keenan, recently told an interviewer, "These are not commercials, they are not three-minute jingles, they're not as easy to get into — this is more like presenting a film." And while it's easy to smirk at his pretension, the parallel is instructive: CD's and films both rely on captive audiences; you've paid your money, so you'll sit still until the end. By contrast MP3's are more like television shows than films: they have to keep you entertained, or you'll click over to something else. If the last track on "10,000 Days" — it's called "Viginti Tres," and it's essentially five minutes of digital groans and sighs — were available as a free download on the Tool site, even hard-core fans probably wouldn't bother with it. Sometimes it's easier to pay attention once you've paid money.

The interstitial music found on CD's also presents a challenge to the iTunes model. (The online store was briefly flummoxed, a few years ago, by a Sonic Youth album track called "Silence"; shoppers eventually won the right to pay 99 cents for 63 seconds of nothing.) In the case of Tool a number of fans have complained online that the new album contains too much atmospheric filler and not enough full-bore songs. No wonder the band doesn't want consumers to cherry-pick.

Flat-fee downloading works best when an album's tracks are roughly equal in length and importance. The Red Hot Chili Peppers, who only recently signed a deal with iTunes, have a new double-CD, "Stadium Arcadium" (Warner Brothers), consisting of discs named "Mars" and "Jupiter." (Sounds as if someone narrowly avoided a lawsuit from John Gray.) Maybe it's a coincidence, but the album is surprisingly iTunes friendly: the structure is loose and the songs are pretty evenly weighted; few grand epics or wispy interludes. Fans can pick and choose, downloading the album piecemeal or compiling favorites to turn the album into a playlist.

It should be no surprise that Tool and many of the other bands resisting iTunes came of age in the 1990's. It was a bull market for music, thanks in part to the high profit margins of CD's. But if you're a younger band and you don't have a loyal army of Toolheads at your disposal, you'll take all the paid downloads you can get.

Musical formats inevitably change the way music is made. The rise of LP's led musicians to think in terms of twinned sets. And despite its seeming formlessness, the CD has shaped music too, although it was harder to appreciate that before MP3's came along. (Nothing helps you love an old product like a new one.) Most people listen to the songs near the start of a CD the most often, and the most intently. A well-organized CD finds subtle ways to accommodate this tendency, and to reward it.

With "10,000 Days" this means many of the sturdiest songs are in the disc's first half. (A decade ago we used to complain about how CD's were front-loaded with the good stuff; now that seems like a sensible, sometimes elegant way to make an album.) Not only the single "Vicarious," but also a glorious, propulsive riff-rock song called "The Pot," which may become a rock hit too.

The CD's second half is a bit more perplexing, the way the second halves of CD's are supposed to be. The mind wanders, the music sometimes meanders; it's not a bad fit. And there's always an uneven rhythm or a transmuting guitar solo to draw you back in. (Especially during that 11-minute song, "Rosetta Stoned.")

In context it's easier to understand "Viginti Tres." It's the digital equivalent of a needle stuck in the empty groove at the end of a record: a gentle reminder that the music is over. And for anyone listening to the CD on repeat, it's a welcome pause before "Vicarious" begins again.

But that's one of the pleasures of CD's: imperfect control. Sure, you could program your CD player to skip your least favorite tracks, or rip the whole thing to MP3's. But sometimes it's easier just to put it in and press play, even if that means you end up hearing some tracks more than you might want to. In one online review of "10,000 Days," a blogger dismissed the final track: "Listened to it once, and that'll probably be the last time." Wanna bet?