The Universal Music Group, the world's largest recording conglomerate, announced today that it will sell many of its songs without attaching copy-protection software to them first. But there's a catch: for now the plan will last only for a few months, and unlocked songs will only be available on select music services.

Universal is casting the decision as an "experiment"; following rival EMI's decision to offer songs free of digital rights management software -- that is, free of software that prevents users from playing songs how they please, on any device they choose -- Universal says it will sell sans-DRM tracks on Real's Rhapsody service, Amazon, Wal-Mart, on artists' Web sites, and Google.

Universal is vowing to monitor piracy during this test. If letting songs go unlocked leads to more file-sharing -- an unimaginable possibility, since today record companies already sells songs completely free of DRM on CDs -- Universal will call off the test.

But iTunes -- which sells, by far, more digital music than any other retailer, much of it protected with DRM that keeps the music locked to iPods -- will get none of Universal's copy-unprotected songs. The company's official position invokes science. iTunes, it says, will be the company's control group: if the DRM-free tracks on other services take off relative to the protected ones on iTunes, then Universal will know it's on to something big.

There's a whole other storyline here too, though. Universal has lately been looking for a way to undermine Apple's power over the music business; for instance, the company wants music publishers to have greater flexibility over pricing their songs than Apple CEO Steve Jobs will allow. In an attempt to gain such power, last month Universal walked away from talks with Apple to renew its contract to sell its music on iTunes.

Will giving DRM-free songs to non-Apple music shops hurt Apple? In theory, perhaps. After all, people will now be able to buy Universal's music for their iPods from places other than iTunes.

But this has been the point all along. Nobody should be locked in to one store because of what device they use to play their songs. With EMI and now Universal coming around to this view, perhaps we might soon live in a such a sensible world.