If you really want an app to do that Doubletwist is a pretty good one. They also have a wireless solution, Airsync. But you could just pop out your SD card, connect it to your PC and drag and drop your files directly to it. Just create a folder on the SD card named "music" and put your files in the folder. The music apps on the phone will find the files. You could also connect your phone to your PC and do the same thing without taking the SD card out. You just need to go to Samsung's website, go to support, look up your phone and download the USB drivers and install them on your PC. If you have downloaded Samsung Kies you already have the drivers installed. Just connect your phone, open Windows Explorer and browse down to your phone and the SD card. Putting the files directly onto your SD card will not carry over any playlists though, you'll have to recreate them on the phone. Another solution is to use Google Music. You download Google Music Manager to your PC, it will find all your music and import it - to include playlists. Then just open The Play Music app on your phone and your music is there for you. This is a streaming service but you can "pin" your music to your phone. By doing that (pin) it caches your music to your phone for offline listening.