Apple has officially released a new version of its hugely successful Internet music download site, iTunes 4.5.

The updated program for Windows and Macintosh possesses the largest commercial catalogue of downloadable files with over 700,000 tracks from five major labels currently available, a number announced yesterday that is expected to swell to over a million in due course.

The iTunes 4.5 also introduces a number of new features aimed at boosting its market dominance.

A range of 150 tracks, exclusive to iTunes, is to be launched offering pre-release singles, such as the Beastie Boys single “Ch-Check It Out”, as well as Disney classics and out of print Motown singles.

An iMix program encourages the mailing and sharing of songs between users, a Party Shuffle function allows music lovers to create their own mixes of tunes, and a Print CD Inserts capability allows owners to fabricate jewel case inserts for albums or mix discs.

A number of other facilities have also been designed including the clever Apple Lossless file, which allows the importation and conversion of music from CDs into iTunes and onto iPods at sound quality indistinguishable from the original.