"We expect more than half of the songs on iTunes will be offered in iTunes Plus versions by the end of this year," Apple CEO Steve Jobs said in a statement.
Apple also noted that more than a dozen of Paul McCartney's classic albums will be available on the Apple music site for the first time.
The DRM-free songs, which feature high-quality 256-Kbps AAC encoding, are offered at $1.29 per song; iTunes will continue to offer its 5 million-plus songs in 128 Kbps AAC encoding at 99 cents a song. Consumers can upgrade previously purchased EMI songs to iTunes Plus tracks for 30 cents a song and about $3 for an album.
Recording artists featured in the DRM-free tracks include singles and albums by Paul McCartney and Wings, Coldplay, The Rolling Stones, Norah Jones, Frank Sinatra, John Coltrane, Joss Stone, and Pink Floyd.
Apple noted that iTunes Plus songs can be played on iPods, Mac and Windows computers, and wide-screen TVs outfitted with Apple TV technology. The company said the songs can also be played on the Apple iPhone, which is scheduled to launch in late June.
Earlier this month, Amazon.com announced that it will launch an online music store that will sell unprotected MP3 songs. "Our MP3-only strategy means all the music that customers buy on Amazon is always DRM-free and plays on any device," Amazon CEO Jeff Bezos said at the time of the announcement.
However, Apple has a commanding lead in online music sales with more than 2.5 billion songs sold to date.