Hi,
It sounds like you are describing a karaoke app? The app can't do this automatically and is beyond the scope of the app.
You would, however, need to manually select each song section either using a foot pedal, or by touching the screen sections as required.
Stage Mode will connect to a Chromecast (wireless display) and show the current section only. Depending on your device, the sound from the pad file may play directly on the cast device, or it may be restricted to your Android device (in which case you would need to connect it to an amplifier).