This enables Songbird users in the US and Europe to buy, download and transfer to portable devices music from 7digital.com's six-million strong MP3 catalogue.
The new integrated service is available at getsongbird.com.
When a track or album is downloaded from 7digital.com in Songbird, it is automatically downloaded into the user's Songbird library.
Users can click the 7digital.com Music Store link in Songbird's left-hand menu to access the store and purchase tracks, without leaving the Songbird application.
"Ben Drury, CEO of 7digital.com, says: "7digital and Songbird is a killer combination for anyone who wants a dynamic, open music player."
Ethan Bauman, director of business development at Songbird, adds: "This is a music lover's dream come true. 320kbps MP3s are downloaded into a library that keeps fans abreast of local band news and gigs, as well as displaying live concert photos, artist bios and more."
Pricing will correspond to pricing on the 7digital website in the country the user lives in.