File content as of revision 0:17458f91a0e9:

#include "mbed.h"

Ticker rhythm;
LocalFileSystem fs("local");  // required even if it appears like it's not used

DigitalIn button(p20);
DigitalOut led(LED1);
AnalogOut headphones(p18);

void myrhythm();
void waitForButton(DigitalOut& led, DigitalIn& button);
void preloadFile(char* clip, int size, const char* path);
void playSound(char* clip, int size, AnalogOut& headphones);

enum
{
    OFF = 0,
    ON = 1
};

enum { MaxWavValue = 255 };

static const float ticker_rhythm = 13E-5;  // 8 kHz sample rate (1/8000 sec delay)
static const char clip_path[] = "/local/blonde.wav";


bool done = false;


void myrhythm()
{
    done = true;
}

int main () 
{
    const int size = 30000;   // 32K max in total (~30K is enough for testing)
    char clip[size];
    
    waitForButton(led, button);
    preloadFile(clip, size, clip_path);
    
    rhythm.attach(&myrhythm, ticker_rhythm);
    
    while (true)
    {        
        waitForButton(led, button);        
        playSound(clip, size, headphones);
    }
}

void waitForButton(DigitalOut& led, DigitalIn& button)
{
  led = ON;
  while (!button) {};
  led = OFF;
}

void preloadFile(char* clip, int size, const char* path)
{
  FILE* file = fopen(path, "r");
  for (int i = 0; i != size; ++i)
    {
      clip[i] = fgetc(file);
    }
  fclose(file);
}

void playSound(char* clip, int size, AnalogOut& headphones)
{
    for (int i= 0; i != size; ++i) 
    {
        while (!done) {};
        done = false;
        headphones = float(clip[i]) / MaxWavValue;
    }
}