This fall Apple will offer iTunes users a paid add-on to its iCloud music syncing called iTunes Match. The service will let you mirror your iTunes library on iCloud, making it possible to access any track on any device you have registered with your Apple ID for a yearly $24.99 subscription fee.

The service has some limitations and perhaps one interesting "loophole," and questions exist concerning what exactly happens when you stop paying $25 every year. We decided to dig in and find out exactly what users can expect when the service rolls out in a few months.

iTunes Match will let you mirror up to 25,000 tracks in your iCloud, and those songs can be pulled down to any iPhone, iPod touch, and iPad, as well as synced with Macs or PCs running iTunes. This includes tracks ripped from CDs or downloaded from the Internet, even those you may have obtained in a less-than-legal manner.

As rumored, Apple's efforts to strike licensing deals with record labels gives its music-in-the-cloud service one major feature over recently announced competing services from Amazon and Google. That feature is the namesake of iTunes Match—using the song match technology acquired from Lala, it scans your iTunes library to find matches among the 18 million tracks in the iTunes Store.

If there is a match found in the iTunes Store catalog, that track is automatically and immediately added to your iCloud store in 256Kbps, DRM-free iTunes Plus format. Even if you have a crappy 128Kbps mp3 rip, if iTunes Match can identify it, you'll immediately have access to the iTunes Plus version.

If there is no match for your obscure French electronica or Detroit garage punk songs, those will be uploaded as-is to your iCloud store. So in theory, you only have to upload a small portion of your collection of music.

The automatic matching is in sharp contrast to Amazon Cloud Player and the Google Music Beta; both those services require all songs to be uploaded, which Apple contends could take weeks. This distinction is what Amazon has claimed absolves them of any need to obtain licenses for its service.

If you don't renew the yearly $25 subscription, your iCloud store goes away. iTunes purchases will still be available to all devices, and anything that you have downloaded from iCloud to your devices you keep. This includes iTunes Plus versions you have chosen to replace older, lower quality rips in your main iTunes library. Apple explained that replacing those lower-quality rips is optional.

Fortune noted that this process presents somewhat of a "loophole" for dirty pirates to essentially pay $25 for "amnesty" of up to 25,000 tracks. We don't entirely agree, though. There doesn't appear to be a reliable way for Apple to know for certain if a particular song has been pirated—barring certain metadata that could be easily stripped out—so really the only benefit is that low-quality rips get replaced with high-quality rips.

A lot of readers asked if Apple shares any information about users' scanned libraries with third parties. Apple tells Ars "no," so the RIAA won't suddenly have a list of every song you ever downloaded or ripped. For the purposes of accounting, though, the company does share aggregate information about which tracks are being added to iCloud via iTunes Match. In other words, EMI will be able to know that 2 million users have Katy Perry's "Teenage Dream" in their library, but not which particular users have it.

Another question our readers asked was what happens if your library is filled with higher quality rips, such as tracks encoded in Apple Lossless (ALAC) format. Matched tracks will still be in 256Kbps iTunes Plus format, while uploaded tracks will retain their original format. Tracks aren't replaced in either your iTunes library or on your devices unless you request them to be, so the lossless files in your main iTunes library will be safe. Sticklers might balk that matched tracks won't be available via iCloud in a higher-quality format, but if you don't require lossless quality on your mobile device, having access to smaller 256kbps AAC files via iCloud may be a benefit.

Our international readers wanted to know if iTunes Match will be available outside of the US. Unfortunately, for now, iTunes Match is limited to US iTunes Store users. While the service may eventually be available to users in other parts of the world, it will require inking agreements with record labels, music publishers, and other rightsholders for each separate country or region. Apple may be in the process of doing that now, but the company said there is nothing to announce regarding availability of iTunes Match outside the US at this time.

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