I made these changes and it compiles+runs nicely.
music.pde && player.cpp -
#include <NewSoftSerial.h> => #include <SoftwareSerial.h>
NewSoftSerial => SoftwareSerial
buffer.h && filesys.cpp -
#include “WProgram.h” => #include <Arduino.h>
buffer.h -
//typedef unsigned char byte; => typedef unsigned char byte;
In music.pde & player.cpp replace the #include and variable definition. Only 4 lines total changed.
In buffer.h && filesys.cpp replace #include. Only 2 lines total changed.
In buffer.h uncomment typedef unsigned char byte; /**< 8 bits, unsigned */. Only 1 line changed