What's growing more quickly: the virtual aisles of Amazon.com (NASDAQ:AMZN), or its portfolio of websites?

Amazon's latest dot-com creation is SoundUnwound.com, a wiki-based music website that lets its users piece together profiles of musical artists. It's not as freely editable as pioneer Wikipedia's music entries; community member edits and submissions are vetted by the site's editorial staff. That's not entirely a bad thing, since even the out-of-control rock and roll world needs rules. Content gets tweaked somewhat anonymously, though the site does rank its most active contributors.

What's in it for Amazon? Money, of course. Artist discographies have links to purchase Amazon MP3 downloads and CDs. Amazon's own website is loaded with music reviews, but this site gives the company one more way to reach out to music lovers.

If Sound Unwound is new music to your ears, join the club. Amazon launched the site on Monday, following the company's purchase of Shelfari, a social networking site for book buffs, last week.

Amazon's approach is sound. While larger retailers like Apple (NASDAQ:AAPL) online and Wal-Mart (NYSE:WMT) offline often take their music storefronts for granted, Amazon's trying to make the most of online music's interactive appeal. Thanks in part to its Amazon Associates program, where third-party publishers receive monthly commission checks for sending business Amazon's way, Amazon recently passed Target (NYSE:TGT) to become the country's fourth-largest music retailer. It now trails only Apple, Wal-Mart, and Best Buy (NYSE:BBY).

Sound Unwound still has plenty of room for improvement. It could take a page out of Google's (NASDAQ:GOOG) Knol playbook by providing financial incentives for its active community members. I'm sure that Amazon can afford to chip in a small commission for each editor of any page whose content results in a CD or MP3 sale. That would certainly inspire starving artists to more actively clean up the site and attract traffic, even if the commissions come as Amazon credit instead of cold hard cash.

All in good time, though. Give the site a chance to grow. For now, Sound Unwound is still at the garage-band stage.

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Longtime Fool contributor Rick Munarriz has been shopping online for about as long as Amazon.com has been in business. He does not own shares in any of the stocks in this article. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.