Apple

  int i;
  int filePlayerCount = 0;

  AUNode   myNode;
  AudioComponentDescription testDescription;

  for (i = 0; i < myNodeCount; i++) {

  result =   AUGraphGetIndNode (
  processingGraph,
  i,
  &myNode
  );

  if (noErr != result) {[self printErrorMessage: @"AUGraphGetIndNode failed" withStatus: result]; return;}

  // Obtain the audio unit instance from its corresponding node.
  result =   AUGraphNodeInfo (
processingGraph,
myNode,
&testDescription,
NULL
);

  if (noErr != result) {[self printErrorMessage: @"AUGraphNodeInfo failed" withStatus: result]; return;}

  if (testDescription.componentSubType == kAudioUnitSubType_AudioFilePlayer) {
  //filePlayerCount++;
  filePlayerCount = filePlayerCount + 1;
  }
  }

  NSLog(@"countFilePlayerNodes is %d", filePlayerCount);