If your phone/tablet has an SD card, there is a MUCH easier way to do this is:
1. Simply unmount your SD card on your device and then remove it
2. Plug the SD card into your computer's card reader
3. Add a folder called "Music" if one doesn't exist on the SD card
4. Move all the songs/albums you want from your Media Player library into the Music folder on the SD card (including album art)
5. Put the SD card back into your device, and your device reads the media on the SD card and you're ready to listen to all the music you just transferred.