Teensy Music Player

void Help() {
  Serial.println(Message);  
  Serial.println("---------------------------------------------------------");
  Serial.println("Thank you for using the Music Player v1.0. ~~ Nischay J. [28th March 2023]");
  Serial.println("The Player is very simple to operate.");
  Serial.println("You operate using single character inputs.");
  Serial.println("The music player will display all available track at startup.");
  Serial.println("At a time only 10 can be selected.");
  Serial.println("Press 'l'(Lowercase L) to display the current 10 selected tracks." );
  Serial.println("To play a specific track, send the track number (0-9).");
  Serial.println("To stop a track, press 's'");  
  Serial.println("Send 'x' to toggle loop of track.");
  Serial.println("To go to the next 10 tracks press 'f' the next 10 tracks will be displayed.");
  Serial.println("To go to the last 10 tracks press 'b' the previous 10 tracks will be displayed.");
  Serial.println("To extend the arm, send 'e'.");
  Serial.println("To retract the arm, send 'r'.");
  Serial.println("Note: The arm is a servo motor and was used to test if the music playing block the Teensy.");
  Serial.println("To see this Help message again, press 'h'.");
  Serial.println("Enjoy your music!");
  Serial.println("---------------------------------------------------------");
}

 char mode = Serial.read();
    // look for the newline. That's the end of your sentence:
    if (Serial.read() == '\n') {}
    //Serial.printf("Read This %c\n", mode);
    switch(mode){
      case 'h':
        Help();
        break;
      case 'x':
        ToggleLoop();
        break;
      case 's':
        Stop();
        break;
      case 'f':
        MyList.Fwd();
        break;
      case 'b':
        MyList.Bwd();
        break;
      case 'l':
        MyList.DisplayCurrentList();
        break;
      #if USE_I2S == 1
      case 'e':
        analogWrite(PIN_SERVOR, ext_pos);
        break;
      case 'r':
        analogWrite(PIN_SERVOR, ret_pos);
        break;
      #endif       
      default:
        int tracknum = MyList.isInList(mode);
        if(tracknum != -1){
          playFile(MyList.SendTrack((uint16_t)tracknum));
        }
        else{
          Serial.println("MP3 Input not Recognized");
        }
        break;
    }

class SongList{
  private:
    char **Songlist = 0;
    uint16_t numsongs;
    uint16_t listsize_r = ListSize;
    uint16_t counter = 0;
    uint16_t counter_limit = 0;
    void initializeSongList();
    void AddMoreListMember(size_t Size);
    char* stringUpper(char* string_in);
  public:
    uint16_t CurrentTrackNo;
    /*
    SongList Class Constructor
    Initializes the list data structure 
    */
    SongList();
    /*
    Displays all the contents in the list. Data is output to the serial port.
    */
    void DisplayListContents();
    /*
    Displays the current 10 tracks that can be selected. The data is output to the serial port.
    */
    void DisplayCurrentList();
    /*
    Finds all the .Wav files in a specified directory. Fills the internal data structure with their name.
    ParameterL rootDir: File pointer to the directory that you want to search the tracks in.
    */
    void SearchSongs(File rootDir);
    /*
    checks if the selected song is in the list. Returns the postiton of the song, otherwise returns -1.
    Parameter: tracknum, a character which should be from 0-9.
    */
    int isInList(char tracknum); 
    /*
    Outputs the track name corresponding to the tracknum selected.
    Parameter: tracknum, uint16_t track number selected to play.
    Returns: pointer to the string containing the track name.
    */
    char* SendTrack(uint16_t tracknum);
    /*
    Moves the internal track selector forward by 10 tracks.
    Outputs the list of track that can be selected.
    Data is output to the serial port.
    */
    void Fwd();
    /*
    Moves the internal track selector backward by 10 tracks.
    Outputs the list of track that can be selected.
    Data is output to the serial port.
    */
    void Bwd();
};