Here is Gondoliere, the best app to get all the music you want.
Just search for any artist or song, and Gondoliere will show you the matching results.
Click on them to stream it on your device.
Check for further instructions on the app.
Note: music is provided by "www.jamendo.com". All songs, available through this application, are intended only for your personal non-commercial use.
Also, not is not possible to download the mp3 file to your device.
Since the music is from authors who give their music for free, you wont find any commercial music here. Please dont give negative ratings just because you dont find what you want.