Japan's wireless operator offers full downloads.
KDDI, Japan's second-largest mobile operator, said that as of Sept. 28, its Chaku-uta Full mobile-music download service had racked up sales of 20 million songs.
The number of tracks downloaded has doubled since June 15 and multiplied ten-fold since February.
Chaku-uta Full, which launched in November 2004, is currently the only service of its kind in Japan.
It features some 60,000 songs and is available through 46 web sites. The number of tracks available has almost doubled since June.
In a statement, the company says that both the number of songs available via Chaku-Uta Full and the number of web sites offering the service will continue to increase.