The rapidly-growing popularity of ringback tunes and mobile-based full-track downloads helped power a 23% rise in digital-music sales in Japan to 111.6 million units in the second quarter.

In value terms, digital sales -- including mobile and PC-based downloads -- rose 40% to ¥17.6 billion ($152 million) in the April-July period, according to data released today by the Recording Industry Assn. of Japan (RIAJ).

Mobile-based master-ringtone sales accumulated by the RIAJ's 46 member companies in the quarter were down 2% from the corresponding period of 2006 to 54.7 million units, for a value of ¥6 billion ($51.6 million), up 1%. However, ringback-tune sales rose 63% to 21.5 million units, for a value of ¥1.5 billion ($13.2 million), marking a 105% rise.

Sales of mobile-based full-track downloads, meanwhile, increased 113% to 25.6 million units, for a value of ¥7.8 billion ($67.6 million), up 102%.

Overall, mobile-based downloads rose 24% to 104.8 million units, for a value of ¥16 billion ($137.9 million), up 41%.

Mobile hits during the April-July quarter included female vocalist Utada Hikaru's single "Flavor of Life" (EMI Music Japan), which since the Jan. 5 release of a master-ringtone version of the track has sold some 7 million units in various digital formats, according to the label.

Universal Music Japan, meanwhile, claims that pop group GreeeeN's "Aiuta (Love Song)," which was released as a physical single on May 16, is the first single anywhere to sell a million full-track mobile downloads. The label says that sales of "Aiuta" in all digital configurations total more than 3 million units.

PC-based music downloads in Japan in the second quarter were up 14% to 6.8 million units, for a value of ¥1.3 billion ($11.2 million), up 3%.

The RIAJ defines the PC-downloads category as comprising singles, albums, mini-albums and "other related content" sold over wired networks, with albums and mini-albums counting as single units regardless of the number of tracks they contain.

The association says that although the data doesn't differentiate between sales of single tracks and albums, singles account for the overwhelming majority of download sales.

The mobile category comprises sales over wireless networks of full single tracks, ring tones, master ring tones and other related content.