Hi everyone! 
After trying all kind of versions, I’ve managed to get Android Sound working by downloading this folder from Github. It works only with WAV or AIF file formats in both Java and Android Mode, but for me this is better than nothing, since I can convert online MP3 files to WAV files at anytime.
So I think this is the best solution I found so far and my project works now very well with this library, so I recommend it to you as well!
Good luck and have fun!
Sammy