I came across this application Songbeat which is a web based music player that runs on your desktop. Songbeat searches for songs that are leagally available on the internet and allows you to play them and even download them.
Is it safe? Is it legal? It is and the Songbeat doesn't need access to your hardrive or music folders. With the free version of Songbeat you get 50 downloads and it's supported by ads but you can get Songbeat Pro by paying €10 for the whole year.
Currently there is only a pc version but a mac version is in the pipelines.