I tried using PROGMEM to store my strings, but I get "multiple definition of" error messages.
I've put prog_char SOUND_TEST_P[] PROGMEM = "Test.wav"; in my "System.h" header file wich is included in many other classes. I presume the later is causing the problem.
But how can I use PROGMEM to store my strings and still be able to use it globally in my Sketch?