New library for PWM playback from SD cards: SimpleSDAudio

Using Arduino Audio
202

Hi again.. used the code below

while (S < 1000) {
    S=(pulseIn(13,HIGH,20000);
    if (millis()-t > 999){p=1;t=millis();
    if (p == 1) {
      SdPlay.setFile("START.AFM"); 
      SdPlay.play();p=0;t=millis();}

and my loop played perfect!!.. BUT now i noticed another problem with pulseIn as i am reading a PWM input to change sounds...

any tips if i can do that? is this an interrupt problem or because changes of the timers? is there anyway to measure PWM while playing sound?