PureSolo is a new application designed for people to sing, or play, along with backing tracks. It's great for drunken Karaoke after lunch on Christmas day, but it's also good for any aspiring musicians - classical or rock & pop - to play along as if they were in a real band.
Each song offered by the service is missing a particular track, be that vocals, guitar, or even oboe or alto sax. When you join you get one free download, but beyond that, each track costs £1 to £2. You can record your efforts with a microphone, and use headphones, too.