I was just thinking of building a web app(for learning purposes) that would let users upload their music files on to a server and then create playlists that could be heard from anywhere in the world by logging in using and i.d. I was also thinking of making it a mobile web app and let people listen to their music by connecting to their internet from their phones.
Is uploading files from a user's PC to a server and playing it back anytime, anywhere, illegal? If the music that was present in the PC were pirated would my app also be a part of the criminal act?