Slacker, which competes with both Pandora and Spotify, relaunched its service in February with a bigger focus on a general-consumer audience as well as mobile listening. Cady told me that Slacker used to be geared towards hardcore music fans, but now tries to appeal to everyone looking for a combination of a curated radio experience and a subscription music service.

That revamp seems to be paying off: the company has added 100,000 paying subscribers as well as a total of six million listeners to the fold. Cady didn’t want to tell me the total number of people who currently pay for Slacker, only stating that it was somewhere between 0.5 and 1 million. But he did point towards a big growth in mobile, with 3.5 million new listeners on mobile devices since the relaunch.

Given that kind of mobile momentum, doubling down on carrier relationships does make sense for Slacker. Cady said that the company already has its app bundled on select handsets, and has billing relationships with all major carriers in place.

He didn’t spell out the details of the upcoming carrier partnership, which Slacker plans to announce in the second half of this year, but the logical next step would be to offer Slacker’s service as a default radio and music package to all subscribers of a certain tier, or even a carrier’s entire customer base.

That’s something the prepaid wireless provider Cricket has pioneered in the US with its Muve Music service. The company has been selling Muve as part of the data plan for all of its Android phones, and it now has more than 1.4 million paying subscribers. 

Another area of growth that Slacker is looking to is automotive integration. Slacker is already part of the Tesla S console, and Cady said that Tesla owners listen two to three times as much as the average Slacker user, with some even clocking more than 100 listening hours a month.

Cady said that the car is an ideal platform for Slacker because it uses a more radio-like model. The service offers curated radio stations with DJS announcing titles, and even has news programming and other non-music content – all of which works great in the car. Said Cady: “People want to listen to more than just music.”

But Slacker, a relative dark horse, is suddenly experiencing some conversion success.

Just last week, the company told Digital Music News that “hundreds of thousands” of listeners are now paying monthly charges of $4 or $5, thanks to direct-billing arrangements through various US-based carriers.

» Read the full post on Digital Music News…

Backed by Centennial Ventures, Rho Ventures, Austin Ventures, Mission Ventures and Sevin Rosen Funds, Slacker just got a fresh influx of roughly $3 million in funding this month, per an SEC filing. Cady told VentureWire that the new money came from “inside investors,” serving as a testament to their faith in the company’s mobile-centric future plans.

Slacker currently has ad-supported Blackberry and iPhone streaming radio apps; it also offers a desktop-based ad-free service for $3.99 per month. The company will continue to sell the G2 through the first half of 2010; it is not clear how long new and existing buyers will be able to get technical support for their devices after that.

Getting people to pay for streaming radio seems to be hard enough, but Slacker faced the bigger hurdle of going head-to-head with Apple’s iPod, an obstacle that even *Microsoft* — with what seems like an infinite budget for marketing, promotion and distribution — has found to be insurmountable. Slacker’s 2-gig and 4-gig G2s retail for $199 and $249, respectively — and that’s a tough sell when compared to the 8-gig iPod Nano, which retails for $149, or the 8-gig iTouch, for $199.

Mudd will remain on the board and actively involved, the story quotes an unnamed investor.