There is no ideal online music store and it's less likely all the time there ever will be. But properly used they can provide some of the greatest moments any music fan experiences.

At their best it's hard to top the immediate gratification of getting a sought-after album or song for pennies on the dollar. Less aware customers, however, can spend vast sums on downloads that turn into nothing more than unplayable files wasting space on a hard drive.

Such services are a better supplement than replacement for traditional albums. Online libraries are inevitably limited and the sound quality of digitally compressed files is inferior to CDs. And of course there's infamous variety of infuriating copy protection methods, which are constantly changing and threatening to leave the computers and portable players of current customers in the dust.

The wise will get the most out of an online music store by following two fairly simple guidelines:

• Subscribing to services allowing permanent downloads of songs in a format compatible with the listener's equipment, not one offering only "streaming" music or "subscription" plans where songs become unplayable when the customer cancels the service.

• Focusing on bargains such as album- and extended-length songs selling at single-song prices (see our online bargains section for specific examples). Related is careful comparison of buying by the song or album; a $10 album may contain four songs—or 20—selling for 99 cents each.

It's also probably a good idea to avoiding signing up for anything requiring a long-term commitment, as services, policies and technology is changing so quickly customers may suddenly find themselves stuck with an unappealing deal. At the moment such requirements are fairly rare.

Some things to consider when comparing services that seem similar in price and selection:

• How many times do they allow a song to be downloaded? Some allow only one, which means the customer has to buy the song again if for some reason it is erased from their computer.

• How restrictive is the copy protection? Some services allow copying of songs to at least a limited number of other computers for listening and/or backup purposes. Also, make sure the file formats are compatible with the computer/audio player you plan to use.

• Is separate software required? Most services will require installing a free program other than a web browser to participate. Does it work with your computer and does it seem simple to use?

• What are the policies about burning CDs? Some don't allow it or limit it to a single burn.

• How useful do the user groups appear to be? The best offer objective reviews and "beat the system" tips like the best and longest tracks for the buck.

The following are the major online music stores as of the summer of 2004, listed roughly in descending order of quality. The exception is author's personal pick, featured at the end since it will likely appeal only to a select group of listeners.

iTunes Music Store

The industry leader for now, but may lose ground as other services more geared to Windows evolve. The selection is vast at more than 700,000 songs and the interface for browsing the collection is perhaps the best. Prices are usually $9.99 for albums and 99 cents for single songs, but newer albums seem to be getting tagged more often with higher price tags. Users must access the store through Apple's iTunes program and downloads are in copy protected AAC format that work with a limited number of programs and portable players. The company has a Microsoft-like habit of issuing mandatory software updates that wreak havoc on the computers and music collections of some users. The indisputable choice for Mac users looking for major artists and releases; Windows users should compare it carefully with the best of the other services.

Walmart Music Store

A highly competitive Windows-only option. Selection, especially of established artists, is top-notch. Songs cost 88 cents each, regardless of how many are on an album. Copy protected Windows Media Audio (WMA) songs only play on Windows PCs and some portable players. Also, some longer songs are not available as single-song purchases.

Napster 2.0

Another fairly good Windows choice, as long as users are aware of its drawbacks—the main one being that songs downloaded on a subscription plan become unplayable if subscriptions expire. Selection matches the best of the others at 700,000 and counting, with files in WMA format. Songs are roughly $1 each, but people purchasing albums need to make sure there are no "omitted" songs—unlike Apple, Napster does not indicate this. A subscription costs $10 a month and allows unlimited downloads (of the kind that expire) and a small discount on regular downloads.

MusicRebellion