Sony and KDDI, Japan's second-largest mobile-phone operator, are joining forces to launch a new music-download service that will allow mobile users to copy onto digital music players tracks they've downloaded from the Internet and stored on handsets.

The two companies said Tuesday (Oct. 16) they will launch the au x Sony Music Project service in December following KDDI's introduction in late November of three new handsets on which the service will be available.

Users will be able to transfer music downloaded from KDDI's EZ Chaku-Uta Full Service to Sony devices such as portable Walkman digital-music players and the Net Juke Walkman-compatible stereo-component system via KDDI's newly developed Lismo Port PC software.

The software also allows copying of songs from CDs and downloading of music to mobile handsets from the "mora for Lismo," PC-based music download service, as well as integrated management of EZ Chaku-Uta Full music files and video clips.

The two Tokyo-based companies say the Project is aimed at expanding Japan's digital-download market, which is overwhelmingly dominated by mobile-based downloads.

In June 2006, Sony and KDDI introduced a mobile handset with a built-in Walkman music player capable of storing some 500 songs.