There's a reason Apple Computer dominates the legal 99-cents-a-download digital music scene: It does it right. Apple's iPods set the style and ease-of-use standards that other portable music players must try (so far unsuccessfully) to match. Its iTunes Music Store and iTunes software are equally unparalleled.

Still, as I wrote in a column on the Napster To Go subscription service, Apple's path isn't the only one that makes sense.

I remain an unabashed iTunes junkie. But an alternative model the "portable" music subscription is growing on me. Now, with the addition of RealNetworks Rhapsody To Go service and especially with the debut this month of Yahoo Music Unlimited I imagine it'll grow on others, too.

I did encounter some sour notes with the two services. Yahoo Music is still in "beta" testing, though the more serious snags actually occurred inside Rhapsody. But overall, both Yahoo and Real left a melodious impression. Each claims more than 1 million songs in its catalogs though they're light on classical. (Apple says iTunes exceeds 1.5 million tracks.)

I'm guessing that Apple will eventually introduce a subscription service of its own.

Why? Under a subscription or rent-a-tune model, you can listen to a boatload of music for a lot less loot than on a buy-only download site. And you can carry those tunes in your pocket, via compatible portable digital music players. Buying 2,000 songs on iTunes would cost nearly 2 grand.

Under Yahoo, you could rent those same tracks for a fraction of that sum. And you can't beat Yahoo's introductory price of $59.88 a year, equal to $4.99 a month. If you prefer to go month to month, you'll fork over $6.99. Subscribers who wish to buy, instead of rent, certain tracks will pay 79 cents each, non-subscribers 99 cents.

At $14.99 a month, Rhapsody To Go is costlier than Yahoo but still a bargain, on a per-song rental basis, compared with iTunes. RealNetworks subscribers can buy downloadable songs for 89 cents a pop. Nice touch: Those who don't subscribe can still listen to 25 full-length "streams" and 25 radio stations a month.

(Napster To Go fetches $14.95 a month and 99 cents a track.)

As with Napster, there's a catch to Real's and Yahoo's rental plans: You must remain a paying subscriber, or the songs you've rented will no longer be playable.

And forget about transferring Yahoo or Real rental tracks to an iPod. (You can still transfer to an iPod songs ripped from CDs and, in Real's case, songs you buy.)

Why rent when you can buy? Aside from the cost savings, you may want to listen to something on a whim. Maybe you're just curious about an emerging artist.

Renting can be complex, though, reflecting conflicts over digital rights. You'll have to buy tunes to burn them to a CD. But some songs can't be bought. Others can be streamed but not downloaded. Some can be downloaded but must stay tethered to a PC. And some can be downloaded and moved to a portable device. Got it?

I prefer Yahoo to Real, and not just because of the lower prices. Yahoo jukebox software (called Yahoo Music Engine) also worked more seamlessly than its Real counterpart. Using both services, I synchronized music with iRiver H10 and RCA Lyra RD2762 devices, though not all tracks ended up on the Lyra. That's because, for now, this model can receive only purchased music, not rented tracks.

When I downloaded or transferred tracks to a portable device, Yahoo displayed a helpful status bar on the Music Engine screen to show the download progress. On Rhapsody, you must visit a separate screen.

Yahoo boasts other sweet touches. Yahoo Music is integrated with Yahoo Messenger. So you can see the music your IM pals are listening to and legally listen along.

You can also search for members who have similar tastes. Members can control who gets to see their collections. People you follow are called "influencers"; their highly rated songs will play on your personalized "LAUNCHcast" radio station. Those who seek your recommendations are deemed "followers."

There were a few annoyances. Yahoo lets you search by album, artist, song or member, though not all at the same time. When I searched Yahoo for certain albums the soundtrack to the movie Fever Pitch, for example Yahoo showed a picture of the album cover and listed the songs. But there was no way to stream any of the album tracks. It happens that Yahoo lacks the rights to play those songs or to make them available for sale. Still, I felt teased.

I ran into bigger trouble with Rhapsody, at least at first. Real's software kept freezing and crashing on an HP Pavilion notebook computer. I called Real for help. Disabling a feature in which Rhapsody is supposed to automatically search for and import new tracks into your music library fixed the problem. But that feature is one that many users will want. Real says a fix will be included in the next release.

What's more, if you decide to buy a track as a Rhapsody subscriber, good luck figuring out how. I had to call the company to determine one way: I right-clicked on a song title and then clicked on the menu item "buy track(s)."

Though Rhapsody doesn't have an instant-messaging component as Yahoo does, there are ways to share and discover free MP3 music. You can press a share button to publish a playlist on Rhapsody, e-mail that list to friends or write a blog about the contents. Rhapsody can show an instant playlist based on songs you've been listening to.

Microsoft's digital rights software underpins both Rhapsody and Yahoo Music. So when something goes wrong with the software, it affects all the music services at once. When "licenses" on my machine somehow became corrupted, rental tracks on Rhapsody and Yahoo failed to play. I had to reinstall Microsoft's software.

I don't expect Apple to slip off the online music throne anytime soon. But Yahoo and Real are at least giving digital music fans plenty to think about.