Seems there's a rush on to provide on-demand, streaming music apps for mobile phones before Spotify hits the market. This time it's Thumbplay, the mobile ringtone powerhouse that today launched a $10 a month streaming music service for both mobile phones and Web users called Thumbplay Music.

While available to anyone online, the mobile app is limited at launch to the BlackBerry platform. Thumbplay executives told Billboard in a pre-briefing that the decision to focus on the Blackberry was twofold: First because the platform has easier-to-use development tools and second, because they wanted to launch on a platform that has less music competition in music services.

Dada Entertainment yesterday launched a similar application called Play.Me, limited to Android devices for now, likely for much the same reason.

The mobile Thumbplay Music app allows unlimited on-demand access to any artist in the catalog, search, the ability to add favorite artists or albums into a quick-find menu, caching capabilities so songs can be played while not in coverage, and wireless synchronization between the user's phone and computer-based apps. It also features an auto-playlist music recommendation generator, and a pretty cool iTunes playlist re-creation tool.

Unlike the Play.Me service from Dada - which lacks content from Warner Music Group - Thumbplay Music has licensing deal with all four major labels, as well as CD Baby, INgrooves, IODA, The Orchard, and several other independent labels.

While both Dada and Thumbplay have a fairly well-established presence in the mobile space, they have no real traction as Web-based service providers other than advertising their ringtone and mobile content services online. That will make it difficult to compete against established online music services for the attention of computer-based users.

But both are betting, instead, on capturing users that are most interested in accessing music on their phones rather than a computer; users who are only interested in occasionally managing their music from their computer.

Which user base is bigger - mobile-focused music fans or computer-focused music fans - is something the entire digital entertainment ecosystem keen to discover.