Hi,
we (2 design-students which never used processing before) are trying to find out how to get the sound playing only once per section. Thx a lot for your help
Here is our code:

import hypermedia.video.*;
boolean sperre=false;

import arb.soundcipher.*;

SoundCipher sc = new SoundCipher(this);





OpenCV opencv;

int w = 1024;
int h = 768;
int threshold = 80;
float[] pitches = {60, 64, 67, 127}; // c major 7th



void setup() {



 size( 1024,768);
 opencv = new OpenCV( this );
 opencv.capture(w,h);
}



void draw() {

 background(0);
 opencv.read();
 opencv.absDiff();
 opencv.threshold(threshold);
 image( opencv.image(OpenCV.GRAY), 0, 0 );



 Blob[] blobs = opencv.blobs( 100, w*h/3, 20, true );




 for( int i=0; i<blobs.length; i++ ) {

   Point centroid = blobs[i].centroid;
   Point[] points = blobs[i].points;


   if(centroid.x>=0  && centroid.x<=128){
 
     sc.playNote(60, 100, 4);//pitch, lautst√§rke,dauer

   }
      if(centroid.x>=129  && centroid.x<=256){
     sc.playNote(61, 100, 4);//pitch, lautst√§rke,dauer
   }
          if(centroid.x>=257  && centroid.x<=384){
     sc.playNote(62, 100, 4);//pitch, lautst√§rke,dauer
   }
              if(centroid.x>=385  && centroid.x<=512){
     sc.playNote(63, 100, 4);//pitch, lautst√§rke,dauer
   }
                  if(centroid.x>=513  && centroid.x<=640){
     sc.playNote(64, 100, 4);//pitch, lautst√§rke,dauer
   }
                      if(centroid.x>=641  && centroid.x<=768){
     sc.playNote(65, 100, 4);//pitch, lautst√§rke,dauer
   }
                        if(centroid.x>=769  && centroid.x<=896){
     sc.playNote(66, 100, 4);//pitch, lautst√§rke,dauer
   }
                          if(centroid.x>=897  && centroid.x<=1024){
     sc.playNote(67, 100, 4);//pitch, lautst√§rke,dauer
   }

 }

 opencv.remember(OpenCV.SOURCE);  



}


public void stop() {
 opencv.stop();
 super.stop();
}