T-Mobile has today doubled the number of streaming music services supported with its recently launched “Music Freedom” program which allows the company’s customers to stream music from a variety of apps without counting towards their data caps. T-Mobile announced this feature in June with a limited number of services, including then only “top” industry players like Pandora, iTunes Radio, iHeartRadio, Spotify, Slacker, Rhapsody and others. Now the company says it has added 14 others, which doubles the number of providers in the program.

The new services include Google Play Music, Xbox Music, SoundCloud, RadioTunes, Live365, Mad Genius Radio, radioPup, radio.com, as well as smaller, specialty services focused on music genres like Fit Radio (for the gym), Fresca Radio (Latin, Hispanic and Caribbean music), Digitally Imported (electronic dance), JAZZRADIO, ROCKRADIO, and Saavn (Bollywood and Indian music).

For T-Mobile customers on a supported data plan – including Simple Choice, Pay in Advance, and some standard plans – Music Freedom allows them to stream music without worrying that they’ll go over their data limits while on T-Mobile’s network. The feature doesn’t kick in when roaming, however, or for streaming over a Mobile Hotspot or while tethered.

While seemingly a good deal for consumers, the launch of the feature did raise some net neutrality-related questions about T-Mobile’s ability to play “gatekeeper” to these streaming music services.* By only selecting a handful of the top players at launch, T-Mobile may have made it more difficult for smaller, niche services to compete while trying to reach T-Mobile’s 49.1 million customers.

For instance, Rdio was not initially available in the program, though it is now, and Beats is still not on T-Mobile’s list – even though iTunes Radio is, and both are Apple-owned. That means some services and their customers are left out of this deal, but that could change in time. T-Mobile says its program will continue to grow and it wants to support “every possible streaming service.”

Plus, rumor has it that Beats will be rolled into Apple’s general iTunes music offerings in the future, which could then allow it to be included. (In fact, its omission here as a standalone line item could be a hint that deal is in the works, given that all the other major music services are already listed and T-Mobile is now moving on to niche players. You can see the full list here.)

T-Mobile says that following this summer’s launch of Music Freedom, the number of T-Mobile customers streaming music daily has jumped nearly 300%, and they’re now streaming 66 million songs – or roughly 200 terabytes of data – per day. 1 in 4 also cited Music Freedom as a key reason they switched carriers, the carrier also claims.

* Update: T-Mobile responded to this saying it’s not a “gatekeeper” here because services are selected by consumer voting and by services themselves asking for inclusion. However, ultimately, T-Mobile is in charge of flipping the proverbial switch and there aren’t regulations around this type of thing at this time. Just because T-Mobile is playing the good guy here today, allowing a carrier to include or exclude individual services from data caps is setting a dangerous precedent with regard to net neutrality. T-Mobile’s move may be a pro-consumer one meant to draw in new subscribers, but from a high level, it’s right to question if carriers should have this sort of power over their networks.