Subscription-based music service eMusic has a new CEO in Adam Klein, as well as plans to revamp its website by the end of the year and launch an ambitious-sounding streaming music service, reports All Things Digital’s Peter Kafka.

Klein’s resume includes stints at media heavyweights like MTV and EMI, as well as the ad startup VideoEgg. He’s replacing Danny Stein, who runs JDS Capital/Management Dimensional Associates (eMusic’s owner), and who in turn replaced former CEO David Pakman almost two years ago.

eMusic’s service works differently from the likes of the iTunes Store or Amazon MP3 — which allow you to purchase individual tracks or whole albums — and all-you-can-eat music streaming services like Rhapsody or Rdio. Instead, the company offers subscription plans that give you a certain amount of credits to spend every month — starting at $11.99 for 24 credits. Unused credits expire monthly (something eMusic relies on to deliver its low prices), and subscribers can also purchase “booster packs” that add more credits should they run out.

The site generates some $65 million a year from 350,000 subscribers — but that’s down from 400,000 a few years ago.

Clearly, eMusic is in an odd spot compared to other music sites, and given the rising popularity of alternative music options, it needs to somehow make itself more appealing to new customers. It recently shifted away from its focus on indie music by adding back catalog music from Warner and Sony. Stein and Klein say they’re planning for a redesigned site in the fourth quarter of this year that will entice non-subscribers to stick around.

More interesting than a shiny new site, however, is the news that eMusic is interested in a streaming “locker” service that would allow subscribers to listen to music they’ve already purchased practically anywhere. The plans still seem unclear, but eMusic says users will be able to stream music to their PCs and mobile devices (Android and iPhone were named specifically), and it may let users stream music purchased outside of the service as well.

The company doesn’t believe it will need to pay the music labels more royalties to offer the service, and it’s unsure if it will charge subscribers more for the privilege. It seems unlikely that the labels will agree with eMusic’s reasoning, but we’ll keep an eye on the situation.