San Francisco start-up Pioneers of the Inevitable has released an early version of its Songbird media player that aims to deliver an open source alternative to iTunes and Windows Media Player. 

The project is labelled the 'Firefox of MP3' in a reference to the success of the Mozilla Foundation's open source browser in eroding Internet Explorer's market share.

"We share the Mozilla Foundation's mission to preserve innovation and choice on the internet," the developers state on their website.

The current version of the application is a 'proof of concept' designed for testing only. It is not meant to replace any current music players, the developers warned.

Songbird supports all popular music formats, including MP3, AAC and WMA. It will not currently play songs that use digital rights management, such as music purchased from the iTunes music store, Yahoo Music or Napster.

The developers plan to add support for DRM-protected Windows Media Audio files in the future, but are unable to expand support to music from the iTunes music store because Apple does not provide the necessary APIs.

Songbird will be able to support multiple online music stores. The preview version provides access to services including Amazon, Audible, Connect and Mp3tunes.