joystick interferes with playback

Hi guys,

I have an interrupt driven MIDI player on my Mega but when ever I use the joystick to navigate through my menu, it interrupts the playback of the MIDI notes.

How do I manage button or joysticks during playback? Is there a hardware driven interrupt (something to handle the joystick & TFT LCD while not interfering with the MIDI playback)?

All of my code is here: