These are interesting times as tech giants beef up their ammo in digital music, but one of the quieter assaults on industry leaders Spotify, Pandora (NYSE:P), and Sirius XM Radio (NASDAQ:SIRI) happened earlier this year when Samsung (NASDAQOTH: SSNLF) introduced Milk Music, powered by Slacker. It's been nearly three months since the world's largest smartphone maker rolled out Milk Music exclusively to Galaxy phone and tablet owners. The Internet radio packs some pretty sweet specs.

  • There are 200 genre stations, more than Sirius XM's receiver-based offering. 
  • The content is curated from a music library that is 13 million songs deep.
  • The service is also free and ad-free -- something that Pandora, Spotify, Sirius XM, and iTunes Radio can't offer -- for a limited time.

There are limitations, of course. It's only available for Galaxy devices in the U.S., but that is a pretty big market given Samsung's stateside success. There's also that tenuous asterisk behind the ad-free service. It points out that the ad-free streaming service is free "for a limited time" and that wouldn't be the case if Samsung was going to make this a permanent feature for Galaxy owners. Then again, it's been three months and Milk Music is still free.

Back in April there was some rumbling when an infographic blog post indicated that a premium ad-free service would roll out soon at $3.99 a month with ads introduced for the free service. Samsung went on to quickly remove that post, but it remains to be seen if it has had a change of heart or if it just showed its hand too quickly. Either way, the asterisk remains. 

The good news for the leading players of digital music is that they are growing in light of Samsung pushing Milk Music. Pandora's 75.3 million unique listeners at the end of February remained unchanged at the end of March and increased to 76 million by the end of April. Sirius XM closed out the first quarter with 266,799 more subscribers, and it expects to add nearly a million more net additions through the balance of the year. Spotify announced last month that it has topped 10 million paying subscribers, three times as many premium members as Pandora. 

It's against this backdrop that Milk Music is hoping that its relative value will make it attractive to Galaxy owners just as Samsung hopes that it's yet another distinctive feature to make it the top choice among Android devices. For now, there's clearly enough market for everybody to grow. However, Sirius XM investors will want to keep an eye on how subscriptions play out throughout 2014 as more Samsung owners begin using Milk Music in their connected cars. Sirius XM's top-notch programming makes it more than a mere music service, but the landscape grows more competitive.