MIDI code when USB port is disconnected

[jrdarrah]

I've created an electronic instrument that uses a MPR121 to read fingerholes. A timer scans for input 256 times a second. This would be fingerholes in manual mode or MIDI.read if in MIDI player mode. Normal operation would be battery powered without a USB connection, however, if there is a USB connection the device can be placed into a MIDI playing mode where the finger holes are disabled for the duration. I see the MIDI.begin but no MIDI.end. What happens if the USB cable is disconnected given I've defined and started a MIDI channel? Would it be enough to prevent the MIDI.read from being executed if I detect that the USB has been disconnected and the instrument is back to playing via battery. If it works properly, the teensy will not lose power so I need to make sure the remnants of the MIDI won't hang the teensy given there is no USB.

MIDI_CREATE_INSTANCE(HardwareSerial, Serial2, MIDI);

in setup ()

	MIDI.begin(MIDI_CHANNEL_OMNI);
	
	usbMIDI.setHandleNoteOff(MIDINoteOff);
        usbMIDI.setHandleNoteOn(MIDINoteOn);
	
in a timer routine that scans for inputs 256 times a second

  if (MIDIState) <-true if the instrument allows MIDI input, right now this doesn't mean the USB is up, just that the player has put the instrument in MIDI player mode
  {
    usbMIDI.read();
  }
  
/**************************************************************************************************************
     Turn midi On
***************************************************************************************************************/
void MIDINoteOn(byte channel, byte note, byte velocity)
{
  if (MIDIPlaying == false)  <- this section of code unmutes the instrument if we are actively playing
  {
    MIDIPlaying = true;
    instrumentUnmuteAll();
  }
  if (MIDIState == true) {
    newNotePlaying = MIDItoNote(note);    <- this converts the midi note number to  a note that can be played through the audio timer code
    MIDIInactivityCounter = 0;                      //reset the counter so we don't cut off sounds
  }

}  //end MIDINoteOn

/**************************************************************************************************************
     Turn midi Off
***************************************************************************************************************/
void MIDINoteOff(byte channel, byte note, byte velocity)
{
  if (MIDIPlaying == false)
  {
    MIDIPlaying = true;
    instrumentUnmuteAll();
  }
  MIDIInactivityCounter = 0;                      //reset the counter so we don't cut off sounds

}  //end MIDINoteOff[
/CODE]