You can play multiple MP3 at the same time using a virtual DJ application like Virtual DJ or use Winamp. Winamp has a feature called Multiple instances. You can activate it by pressing CTRL+P to access Preferences, then follow the instructions in the image attached. Enable the setting and then you can open multiple instances of the same application. Add tracks to all instances and you can play them both. A soundcard with 7.1 capability is required.