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Interactive music always sounds like a cosmically wonderful idea. Transform your computer from a mundane workday tool into a musical instrument! Make your keyboard sing! Jam till your wrists ache! Surf an ocean of sound!

Like all promises of technological enlightenment, this one rarely delivers. Bugs trip you up. Sounds are out of sync. Interactivity suddenly hits walls; that ocean of sound feels like a piddling puddle.

Still, technology marches on, and the range of possibilities for desktop-dabbler musicians today keeps getting broader and deeper. Just compare Peter Gabriel's new CD-ROM, "Eve," with its 3-year-old predecessor, "Xplora 1: Peter Gabriel's Secret World." "Xplora" was smart and tasteful and groundbreaking in its time, but it couldn't hide its own hodgepodge confusion over whether it was personal statement, fan scrapbook or multimedia experiment. "Eve," by comparison, arrives as a confident, state-of-the-art contribution to the multimedia genre. Love it or not, there's no mistaking it for a promotional brochure.

At the heart of "Eve" lie a series of "Interactive Musical Xperiences," or musical toys -- screens that strip down popular Gabriel tunes like "In Your Eyes," "Come Talk To Me" and "Shaking the Tree" to layers of tracks, riffs and dubs and let you goof around with reassembling them, recording your own mixes and translating them into animated videos. Gabriel and his collaborators (at his own Real World company and at Starwave) plainly took great care in building these mix-your-own environments out of chunks of Gabriel's sound and the imagery of "Eve's" four visual artists; the screens are beautiful, the sounds lush, the transitions seamless.

But "Eve" isn't all jam-along toys; to get to play around you have to wander through the CD-ROM's landscapes, collecting musical samples embedded in symbolic tableaux of mud and gravel, hidden in fields of greenery and hanging in galleries. Using the 360-degree wraparound panoramas of Quicktime VR to expand on the visual vocabulary of "Myst," "Eve" buries its musical improvs in an interactive puzzle-world that mutates around you as it remixes images from the Book of Genesis and genetics to make a murky commentary on sexual relations. Occasionally some psychologist or artist will pop up to offer sound-bite insights. Once you've listened enough, clicked enough or simply hung out long enough, "Eve's" folds recede a notch and let you in deeper. You can't have any uncertainty about the sexual nature of this design -- or its casting of the player as the lost male in search of the eternal feminine Other; in its very first demand on you, "Eve" turns the cursor into a sperm and requires that you penetrate an ovum to proceed.

So you can't just wade in and play; you have to earn the right. According to Gabriel's therapeutic ethos, I suppose this can be described as requiring users to "take a journey" before they can mess around. You can't have your fun until you, like, grow.

Viewed from a different angle, though, the requirement of mastering one screen before you can move on to the next is also a little puritanical. Interactive music appeals to people who never subjected themselves to the discipline of mastering musical notation or learning an instrument; "Eve" removes those hurdles -- and then immediately replaces them with new ones from the genre of puzzle-games like "Myst" and "The Seventh Guest" (the piece also owes different kinds of debts to important previous CD-ROMs like "Scrutiny in the Great Round," "Meet MediaBand" and Laurie Anderson's "Puppet Motel").

These obstacles can be serious. You may spend many hours with "Eve," as I have, and still, despite all the hints the disk provides, hit a roadblock you can't get past. I still haven't explored the interactive screen for "In Your Eyes" -- and at this rate, I may never.

Compare this approach to the more generous stance of Todd Robbins, creator of "Sound Toy." This elegant, self-deprecatingly-named noise machine is an onscreen grid that, under mouse stimulation, produces exquisitely playful blues tones, walking bass lines and harmonica squeals.

"Sound Toy" was one of the winners of the original New Voices, New Visions contests sponsored by Interval, Voyager and Wired, and last year Voyager published a full CD-ROM collection of Robbins' creations called "Sound Toys." Besides providing audio feedback to screen input, Robbins' "Sound Toys" don't do much. But you don't have to fight or puzzle your way to their secrets; instead, they seduce you into messing around with their gently addictive pleasures.

Interactive music software runs a spectrum of control: At one end lie products like "Eve," in which an artist hands a few tools over to you but remains essentially in charge (you can always recognize the result as Peter Gabriel's sound). But stretching away toward the spectrum's other end are products that turn more and more power over to you, letting you shape not only sequences but sounds, tempos and arrangements. Robbins' "Sound Toys" are freer-form than Gabriel's, but their sounds are still essentially chosen by the creator -- and hearing what funky combinations he devises is part of their pleasure.

A greater degree of precise control over your arrangements is offered by the Mixman CD-ROMs -- software that turns your computer into a DJ console, allowing you to remix tracks from song collections Mixman provides ("Spin Control" is based on San Francisco club music, "Mixman" on rap and hip-hop sounds, and a George Clinton disk is forthcoming). Though Mixman locks you into the genres of music it has pre-selected -- genres that already embrace the remix as a form of art -- in most other ways it gets out of the way and gives you a remarkable amount of control over levels, tempo, pitch and more, across multiple tracks.

If you're really after the full joys of free play, though, you have to turn to the children's software shelf, where two exemplary products offer contrasting but complementary versions of the interactive musical sandbox. Maxis' "SimTunes" and Voyager's "Making Music" each create free environments for kids (and adults) to make their own music on the computer desktop while learning about composition in the process.

"Making Music" is the more rigorous of the two. Composer Morton Subotnick's software provides a scratch pad for writing and revising musical pieces. As you use it you receive a painless and sometimes inspiring introduction to scales, harmony, rhythm, counterpoint and orchestration -- the bones beneath music's skin.

For sheer delight, though, it's impossible to beat Japanese artist Toshio Iwai's "SimTunes," in which animated "Bugz" crawl across screens you paint and make enticing rhythms and melodies as their tracks cross the color zones you lay out. It's a deceptively simple interface for a surprisingly complex syncopation tool that addictively links visual play with musical creation; you can play it free-form or use a variety of pre-supplied patterns. Part "PacMan," part light organ and part synthesizer, "SimTunes" is a pure-fun machine.

Each of these products invents its own system for transforming a computer into a music-making device that's nothing like any traditional musical instrument. It's getting easier and cheaper, too, to get your computer to mimic a conventional synthesizer; near-professional-quality MIDI software that used to cost hundreds if not thousands of dollars keeps becoming more accessible. At $99, for instance, CyberSound Studio provides you with a sequencer, a high-quality palette of sounds and even a (not terribly high-quality) keyboard. The instant-gratification level isn't as high as with some other sound toys, but you gain a much broader sonic canvas and much more precise tools for filling it.

One drawback that bedevils some of these products (and that Mac users will still find troubling with CyberSound) is called "the latency problem" -- a fancy way of describing a tiny but perceptible delay between when you hit a note and when the computer plays it. The problem is a lot less severe than it was with early efforts in this genre, like the music-making CD-ROM "Rock, Rap and Roll" (which later evolved into "Rock 'n' Roll Your Own"). But it's still disconcerting.

Still, the latency problem on your desktop is nothing compared to the latency problem across the Net, where experiments in interactive music are just beginning to multiply. The Microsoft Network has been smart enough to understand the potential in this form, but not quite smart enough to pull it off. Its Rifff site (accessible only to MSN members) promises to let you "jam" with different artists each week -- or at least remix their recordings. Works by Jane Siberry and Robyn Hitchcock were recently featured, so there's some unconventionality to the programming. Trouble is, I waited a good half-hour trying to download all the elements to Rifff over my 28.8 modem, yet despite repeated tries could not get the site to work. Ironically, the only computers with fast enough Internet connections to make Rifff useful are those sitting in people's offices -- which is probably not where most potential users have the time (or the job security) to jam.

In any case, what Rifff delivers online is very similar to what's already available on CD-ROM. The real future of interactive music on the Net lies not in such repurposing of celebrity (or sub-celebrity) content but in real collaboration between people in different places -- Net-based equivalents of pick-up bands, open mikes, park-bench sing-alongs and similar forms of communal music-making. The technology still has a long way to go, but it's inevitable that it will arrive, leaving sites like Rifff far behind.

In fact, the more time you spend with truly interactive music software that casts you more as composer than as listener, the harder it is to find serious diversion in the more limited range of possibilities provided by Gabriel's "Eve." It's not enough for an artist to invite us into a world but then severely constrain what we can do there. Of course, we'll never give up listening to music and looking at images created by inspired artists. Why would we want to? But when we feel like playing around ourselves, we will expect more than the spare parts for a few remixes.