diff -r 0b01cbd8ed9e -r 44320144951a client/annotviz/app/js/pianoroll.js
--- a/client/annotviz/app/js/pianoroll.js	Fri Apr 17 11:48:03 2015 +0200
+++ b/client/annotviz/app/js/pianoroll.js	Mon Jan 26 09:32:01 2015 +0100
@@ -5,6 +5,10 @@
 *
 */
 
+//TODO: add delay to adjust the "zero". this could should be given as an option
+//or if explicitely null automatically adjusted from the mean of difference
+//between the note timestamp and the current timestamp.
+
 'use strict';
 
 
@@ -84,6 +88,10 @@
         var channel = data.content[2];
         var sessionTs = data.content[1];
 
+        if(velocity !== 0 && typeof(this.noteDict[channel]) !== 'undefined' && typeof(this.noteDict[channel][note] !== 'undefined')) {
+            this.addNote(note, ts, sessionTs, 0, channel, 0);
+        }
+
         this.addNote(note, ts, sessionTs, velocity, channel, 0);
     };