iTunes sold 20 million tracks in its first seven months of operation. Rhapsody?s 250,000 subscribers paid to listen to 28 million songs in October, up from 11 million in June. Between June and November, music lovers bought 7.7 million songs online, but only 4 million single-song CDs at stores. The future looks good, too. Jupiter Research expects online music sales to grow to $3.3 billion by 2008. Forrester Research, for its part, expects that within just four years online music will account for 33% of the music industry?s sales.