Btopenworld, the internet strand of the communications company, has built a customised player based on Microsoft's Windows Media Player 7 to supply online music for its users.
The service is currently being trialled alongside a research programme in an attempt to ensure it is useable and attractive to consumers.
The venture is one of several high-profile internet music subscription services hoping to fill the gap left by Napster, which is currently off-line due to legal wranglings.
Btopenworld has hooked up with leading UK record companies including BMG Entertainment, V2 and Warner Music, to offer music from artists such as Dido, Stereophonics and David Gray.
'Powerful'
Chief operating officer Ben Andradi said: "The powerful and easy-to-use Windows Media Player is an important component in our delivery of the UK's first secure music subscription service offering the best possible music experience to our customers
"Btopenworld is putting together the right combination of great music and great technology to deliver a powerful service for music fans."
The big music companies are also aiming to launch their own download services by the end of the year.
MusicNet is the joint venture between BMG, EMI and Warner, while Pressplay is backed by Sony and Universal.
Napster has also promised its users it will be up and running with a subscription-based website by the New Year, after settling claims for compensation from the music industry for using of copyrighted material.
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