Sony BMG is apparently working on an online music subscription service designed to be compatible with a wide range of portable music players including Apple’s iPod product line. The news comes from Sony BMG Music Entertaiment CEO Rolf Schmidt-Holtz, according to Yahoo! Finance.

While Mr. Schmidt-Holtz was willing to say that Sony is developing a subscription service, he wasn’t willing to share when consumers should expect the service to launch.

Pricing for the service hasn’t been set yet, either, but Mr. Schmidt-Holtz said the "simplest option would be a flat rate." That rate will likely fall somewhere between Û6 and Û8 (about US$9.334 to $12.46) per month for unlimited access to Sony BMG’s complete music catalog.

The record label may also be considering other music distributors in its subscription plan.

So far, music subscription services haven’t been able to compete with the popularity of Apple’s iTunes Store which lets users purchase songs instead of rent them. Sony may, however, have a twist that could help its subscription service compete with the iTunes Store. According to Mr. Schmidt-Holtz, it’s possible "that clients could keep some songs indefinitely, that they would own them even after the subscription expired."

Just how Sony’s rent some, keep some plan would work remains to be seen, especially since consumers seem to be more interested in digital music purchases instead of rentals right now.