diff --git a/src/jsAudioWorkletMain/kotlin/WorkletProcessor.kt b/src/jsAudioWorkletMain/kotlin/WorkletProcessor.kt
index 838fcf5..cfbeb0a 100644
--- a/src/jsAudioWorkletMain/kotlin/WorkletProcessor.kt
+++ b/src/jsAudioWorkletMain/kotlin/WorkletProcessor.kt
@@ -12,13 +12,15 @@ const val PI2 = PI * 2
 @ExperimentalJsExport
 @JsExport
 object WorkletProcessor {
-  var port: MessagePort? = null
+  private var port: MessagePort? = null
 
-  var counter: Int = 0
-  var note = Note.C2
-  var offset = 0.0
+  private var counter: Int = 0
+  private var note = Note.C2
+  private var offset = 0.0
 
-  var note_length = 2500
+  private var started = false
+  private var note_length = 2500
+  private var harmonics = 3
 
   @JsName("setPort")
   fun setPort(port: MessagePort) {
@@ -36,16 +38,20 @@ object WorkletProcessor {
       when (parts[0]) {
         "start" -> {
           println("Start worklet!")
-        }
 
+          started = true
+        }
         "stop" -> {
+          println("Stop worklet!")
 
+          started = false
         }
-
         "set_note_length" -> {
           note_length = parts[1].toInt()
         }
-
+        "harmonics" -> {
+          harmonics = parts[1].toInt()
+        }
         else ->
           console.error("Don't kow how to handle message", message)
       }
@@ -54,34 +60,37 @@ object WorkletProcessor {
 
   @JsName("process")
   fun process(samples: Int, left: Float64Array, right: Float64Array) {
-    var tmpCounter = counter
-    var delta = note.sampleDelta
+    if (started) {
+      var tmpCounter = counter
+      var delta = note.sampleDelta
 
-    for (sample in 0 until samples) {
-      var value = sin(offset * PI2) +
-          sin(offset * 2 * PI2) * 0.6 +
-          sin(offset * 3 * PI2) * 0.4 +
-          sin(offset * 4 * PI2) * 0.3
-      offset += delta
+      for (sample in 0 until samples) {
+        var value = sin(offset * PI2);
 
-      // new note every NOTE_LENGTH samples
-      val noteProgress = tmpCounter % note_length
-      if (noteProgress == 0) {
-        note = note.transpose(1)
-        if (note == Note.C7) {
-          note = Note.C2
+        for(index in 0 until harmonics) {
+          value += sin(offset * (index + 2) * PI2) * (1.0 / (index+2))
         }
-        delta = note.sampleDelta
+        offset += delta
+
+        // new note every NOTE_LENGTH samples
+        val noteProgress = tmpCounter % note_length
+        if (noteProgress == 0) {
+          note = note.transpose(1)
+          if (note == Note.C7) {
+            note = Note.C2
+          }
+          delta = note.sampleDelta
+        }
+        // simple envelop from max to 0 every note
+        value *= (1.0 - noteProgress / note_length.toDouble())
+
+        left[sample] = value
+        right[sample] = value
+        tmpCounter++
       }
-      // simple envelop from max to 0 every note
-      value *= (1.0 - noteProgress / note_length.toDouble())
 
-      left[sample] = value
-      right[sample] = value
-      tmpCounter++
+      counter += samples
     }
-
-    counter += samples
   }
 
 }
diff --git a/src/jsAudioWorkletMain/kotlin/nl/astraeus/processor/WorkletProcessor.kt b/src/jsAudioWorkletMain/kotlin/nl/astraeus/processor/WorkletProcessor.kt
deleted file mode 100644
index 85a3c7d..0000000
--- a/src/jsAudioWorkletMain/kotlin/nl/astraeus/processor/WorkletProcessor.kt
+++ /dev/null
@@ -1,46 +0,0 @@
-@file:OptIn(ExperimentalJsExport::class)
-
-package nl.astraeus.processor
-
-import org.khronos.webgl.Float64Array
-import org.w3c.dom.MessageEvent
-import org.w3c.dom.MessagePort
-
-@ExperimentalJsExport
-@JsExport
-object WorkletProcessor {
-  var port: MessagePort? = null
-
-  @JsName("setPort")
-  fun setPort(port: MessagePort) {
-    this.port = port
-    this.port?.onmessage = ::onMessage
-  }
-
-  @JsName("onMessage")
-  fun onMessage(message: MessageEvent) {
-    console.log("WorkletProcessor: Received message", message)
-
-    when (message.data) {
-      "start" -> {
-        println("Start worklet!")
-      }
-      "stop" -> {
-
-      }
-      else ->
-        console.error("Don't kow how to handle message", message)
-    }
-  }
-
-  @JsName("process")
-  fun process(samples: Int, left: Float64Array, right: Float64Array) {
-    //console.log("WorkletProcessor.process", samples)
-//    val buffer = Float64SampleBuffer(samples, left, right)
-//
-//    audioGenerator?.also { generator ->
-//      generator.fillBuffer(buffer, 0, samples, false)
-//    }
-  }
-
-}
diff --git a/src/jsMain/kotlin/nl/astraeus/Main.kt b/src/jsMain/kotlin/nl/astraeus/Main.kt
index 886bec3..9165460 100644
--- a/src/jsMain/kotlin/nl/astraeus/Main.kt
+++ b/src/jsMain/kotlin/nl/astraeus/Main.kt
@@ -9,16 +9,26 @@ fun main() {
 
   println("Ok")
 
-  document.getElementById("clicker")?.also {
+  document.getElementById("startButton")?.also {
     it.addEventListener("click", {
-      AudioWorkletHandler.createContext {
-        println("Created context")
+      if (AudioWorkletHandler.audioContext == null) {
+        AudioWorkletHandler.createContext {
+          println("Created context")
 
+          AudioWorkletHandler.start()
+        }
+      } else {
         AudioWorkletHandler.start()
       }
     }, "")
   }
 
+  document.getElementById("stopButton")?.also {
+    it.addEventListener("click", {
+        AudioWorkletHandler.stop()
+    }, "")
+  }
+
   document.getElementById("noteLength")?.also {
     it.addEventListener("change", {
       val target = it.target
@@ -27,5 +37,13 @@ fun main() {
       }
     }, "")
   }
+  document.getElementById("harmonics")?.also {
+    it.addEventListener("change", {
+      val target = it.target
+      if (target is HTMLInputElement) {
+        AudioWorkletHandler.setHarmonics(target.value.toInt())
+      }
+    }, "")
+  }
 
 }
diff --git a/src/jsMain/kotlin/nl/astraeus/handler/AudioWorkletHandler.kt b/src/jsMain/kotlin/nl/astraeus/handler/AudioWorkletHandler.kt
index 4d211a8..d8d4515 100644
--- a/src/jsMain/kotlin/nl/astraeus/handler/AudioWorkletHandler.kt
+++ b/src/jsMain/kotlin/nl/astraeus/handler/AudioWorkletHandler.kt
@@ -159,7 +159,15 @@ object AudioWorkletHandler : AudioWorklet(
     audioWorkletMessagePort?.postMessage("start")
   }
 
+  fun stop() {
+    audioWorkletMessagePort?.postMessage("stop")
+  }
+
   fun setNoteLength(length: Int) {
     audioWorkletMessagePort?.postMessage("set_note_length\n$length")
   }
+
+  fun setHarmonics(length: Int) {
+    audioWorkletMessagePort?.postMessage("harmonics\n$length")
+  }
 }
diff --git a/src/jsMain/resources/worklet.css b/src/jsMain/resources/worklet.css
index 08e3dec..535f382 100644
--- a/src/jsMain/resources/worklet.css
+++ b/src/jsMain/resources/worklet.css
@@ -1,14 +1,21 @@
+body {
+    font-size: x-large;
+    margin: 2em;
+}
+
 .button_div {
-    margin: 1em;
+    margin: 0.5em;
 }
 
 .button {
     padding: 3px 5px;
     background-color: #2c008f;
     color: white;
-    font-size: large;
+    font-size: xx-large;
+    margin: 0.5em;
 }
 
 input {
     margin: 1em;
+    font-size: x-large;
 }
diff --git a/src/jvmMain/kotlin/Server.kt b/src/jvmMain/kotlin/Server.kt
index 90ab5b9..32d5665 100644
--- a/src/jvmMain/kotlin/Server.kt
+++ b/src/jvmMain/kotlin/Server.kt
@@ -14,14 +14,20 @@ fun HTML.index() {
   }
   body {
     div {
-      +"We need a button to start because we can only start audio from a user event"
+      +"We need a button to start because we can only start audio from a user event:"
     }
     div("button_div") {
       span("button") {
-        id = "clicker"
+        id = "startButton"
 
         +"Start"
       }
+
+      span("button") {
+        id = "stopButton"
+
+        +"Stop"
+      }
     }
     div {
       + "An example of how to interact with the audioworklet:"
@@ -40,6 +46,19 @@ fun HTML.index() {
         step = "100"
       }
     }
+    div {
+      label {
+        htmlFor = "harmonics"
+        +"Number of harmonics:"
+      }
+      input {
+        id = "harmonics"
+        type = InputType.number
+        value = "3"
+        min = "1"
+        max = "10"
+      }
+    }
     script(src = "/static/kotlin-audioworklet.js") {}
   }
 }