Apple iTunes competitor eMusic says its music catalogue now exceeds four million tracks.

eMusic specialises in independent artists and labels, and focuses on music buyers older than 25 years of age. The service's roster features more than 40,000 record labels, the majority of which are available worldwide, according to the company.

eMusic sells music in MP3 format, which is playable by iTunes and other music players, and can also work on the iPod. eMusic doesn't use any Digital Rights Management (DRM) technology to protect its songs, so you're free to do what you want with the music you download.

While the iTunes Store operates on an 'a la carte' basis for the most part, enabling you to buy individual songs and albums, eMusic operates on a subscription model: Users pay a monthly fee that enables them to download up to a specific number of songs (determined by the fee they pay).