Simple example of playing a sequence of tracks.

MP3sequence.ino

// libraries
#include <SPI.h>
#include <SdFat.h>
#include <SdFatUtil.h>
#include <SFEMP3Shield.h>

// initialize MP3 card
SdFat sd;
SFEMP3Shield MP3player;
byte result; // variable for mp3 player shield, can be used to debug

// setup
void setup() {

  if(!sd.begin(9, SPI_HALF_SPEED)) sd.initErrorHalt();
  if (!sd.chdir("/")) sd.errorHalt("sd.chdir");
  MP3player.begin();
  MP3player.setVolume(10,10);
}

// loop
void loop() {
  for (int i=0; i <= 255; i++) {
    if(!MP3player.playTrack(i)) { // if it returns an error move on to next track.
      while (MP3player.isPlaying());
      MP3player.stopTrack();
    }
  }
}