Songza started life as a music search engine, before going quiet after rightsholders started flexing their legal muscles in response. Now it’s returned as a different service focusing on social radio. The idea: people create online radio stations and then let their friends, family and colleagues chip in to shape the music that it plays. Songza claims to have a catalogue of more than eight million tracks. The service is free, and appears to have a business model based around advertising.