The ad-supported free digital music service SpiralFrog has taken a step closer to finally going live. The company this week initiated an invite-only beta launch in Canada and the U.S., inviting select media and other outlets to test the service and provide feedback.

The service currently has a deal in place with Universal Music Group and has approximately 770,000 tracks and more than 3,500 music videos available. The video portion of the service allows users to both stream and download their music videos of choice.

The ad-supported model requires users to watch ads while their songs or videos are downloaded. Each download takes about 90 seconds, during which time a variety of ads and promotional content will air.

All the music is protected in Windows Media Audio DRM, meaning it cannot play on the iPod.

SpiralFrog's initial launch date was last December, which it obviously missed. The company's CEO Robin Kent and a number of directors left this spring. It now expects to emerge from the private beta for a public launch by the end of the summer.