Touch_MP3 but without the ability to trigger another track while one is currently playing

Touch_MP3_no_trigger_while_playing

/*******************************************************************************
 Bare Conductive Touch MP3 player
 ------------------------------
 
 Touch_MP3.ino - touch triggered MP3 playback
 You need twelve MP3 files named TRACK000.mp3 to TRACK011.mp3 in the root of the 
 microSD card. 
 
 When you touch electrode E0, TRACK000.mp3 will play. When you touch electrode 
 E1, TRACK001.mp3 will play, and so on.
  SD card    
  │
    TRACK000.mp3  
    TRACK001.mp3  
    TRACK002.mp3  
    TRACK003.mp3  
    TRACK004.mp3  
    TRACK005.mp3  
    TRACK006.mp3  
    TRACK007.mp3  
    TRACK008.mp3  
    TRACK009.mp3  
    TRACK010.mp3  
    TRACK011.mp3  
 
 Based on code by Jim Lindblom and plenty of inspiration from the Freescale 
 Semiconductor datasheets and application notes.
 
 Bare Conductive code written by Stefan Dzisiewski-Smith and Peter Krige.
 
 This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 
 Unported License (CC BY-SA 3.0) http://creativecommons.org/licenses/by-sa/3.0/
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
*******************************************************************************/

// compiler error handling
#include "Compiler_Errors.h"

// touch includes
#include <MPR121.h>
#include <Wire.h>
#define MPR121_ADDR 0x5C
#define MPR121_INT 4

// mp3 includes
#include <SPI.h>
#include <SdFat.h>
#include <SdFatUtil.h> 
#include <SFEMP3Shield.h>

// mp3 variables
SFEMP3Shield MP3player;
byte result;
int lastPlayed = 0;

// mp3 behaviour defines
#define REPLAY_MODE TRUE  // By default, touching an electrode repeatedly will 
                          // play the track again from the start each time.
                          //
                          // If you set this to FALSE, repeatedly touching an 
                          // electrode will stop the track if it is already 
                          // playing, or play it from the start if it is not.

// touch behaviour definitions
#define firstPin 0
#define lastPin 11

// sd card instantiation
SdFat sd;

void setup(){  
  Serial.begin(57600);
  
  pinMode(LED_BUILTIN, OUTPUT);
   
  //while (!Serial) ; {} //uncomment when using the serial monitor 
  Serial.println("Bare Conductive Touch MP3 player");

  if(!sd.begin(SD_SEL, SPI_HALF_SPEED)) sd.initErrorHalt();

  if(!MPR121.begin(MPR121_ADDR)) Serial.println("error setting up MPR121");
  MPR121.setInterruptPin(MPR121_INT);

  MPR121.setTouchThreshold(40);
  MPR121.setReleaseThreshold(20);

  result = MP3player.begin();
  MP3player.setVolume(10,10);
 
  if(result != 0) {
    Serial.print("Error code: ");
    Serial.print(result);
    Serial.println(" when trying to start MP3 player");
   }
   
}

void loop(){
  readTouchInputs();
}


void readTouchInputs(){
  if(MPR121.touchStatusChanged()){
    
    MPR121.updateTouchData();

    // only make an action if we have one or fewer pins touched
    // ignore multiple touches
    
    if(MPR121.getNumTouches()<=1){
      for (int i=0; i < 12; i++){  // Check which electrodes were pressed
        if(MPR121.isNewTouch(i)){
        
            //pin i was just touched
            Serial.print("pin ");
            Serial.print(i);
            Serial.println(" was just touched");
            digitalWrite(LED_BUILTIN, HIGH);
            
            if(i<=lastPin && i>=firstPin){
              if(MP3player.isPlaying()){
//                if(lastPlayed==i && !REPLAY_MODE){
//                  // if we're already playing the requested track, stop it
//                  // (but only if we're in REPLAY_MODE)
//                  MP3player.stopTrack();
//                  Serial.print("stopping track ");
//                  Serial.println(i-firstPin);
//                } else {
//                  // if we're already playing a different track (or we're in
//                  // REPLAY_MODE), stop and play the newly requested one
//                  MP3player.stopTrack();
//                  MP3player.playTrack(i-firstPin);
//                  Serial.print("playing track ");
//                  Serial.println(i-firstPin);
//                  
//                  // don't forget to update lastPlayed - without it we don't
//                  // have a history
//                  lastPlayed = i;
//                }
              } else {
                // if we're playing nothing, play the requested track 
                // and update lastplayed
                MP3player.playTrack(i-firstPin);
                Serial.print("playing track ");
                Serial.println(i-firstPin);
                lastPlayed = i;
              }
            }     
        }else{
          if(MPR121.isNewRelease(i)){
            Serial.print("pin ");
            Serial.print(i);
            Serial.println(" is no longer being touched");
            digitalWrite(LED_BUILTIN, LOW);
         } 
        }
      }
    }
  }
}