diff --git a/libs/microbit/music.ts b/libs/microbit/music.ts
index 9426519a..a02ace40 100644
--- a/libs/microbit/music.ts
+++ b/libs/microbit/music.ts
@@ -157,6 +157,10 @@ namespace music {
     export function noteFrequency(name: Notes): number {
         return name;
     }
+    
+    function init() {
+        if (beatsPerMinute <= 0) beatsPerMinute = 120;        
+    }
 
     /**
      * Returns the duration of a beat in milli-seconds
@@ -164,6 +168,7 @@ namespace music {
     //% help=/functions/beat weight=49
     //% blockId=device_beat block="%fraction|beat"
     export function beat(fraction : BeatFraction = BeatFraction.Whole): number {
+        init();
         let beat = 60000 / beatsPerMinute;
         if (fraction == BeatFraction.Whole) return beat;
         else if (fraction == BeatFraction.Half) return beat / 2;
@@ -178,6 +183,7 @@ namespace music {
     //% help=/functions/tempo weight=40
     //% blockId=device_tempo block="tempo (bpm)" blockGap=8
     export function tempo(): number {
+        init();
         return beatsPerMinute;
     }
 
@@ -188,7 +194,7 @@ namespace music {
     //% help=/functions/tempo weight=39
     //% blockId=device_change_tempo block="change tempo by (bpm)|%value" blockGap=8
     export function changeTempoBy(bpm: number): void {
-        setTempo(beatsPerMinute + bpm);
+        setTempo(beat(BeatFraction.Whole) + bpm);
     }
 
     /**
@@ -198,6 +204,7 @@ namespace music {
     //% help=/functions/tempo weight=38
     //% blockId=device_set_tempo block="set tempo to (bpm)|%value"
     export function setTempo(bpm: number): void {
+        init();
         if (bpm > 0) {
             beatsPerMinute = Math.max(1, bpm);
         }
diff --git a/sim/libmbit.ts b/sim/libmbit.ts
index 3cb00c7b..837f38a1 100644
--- a/sim/libmbit.ts
+++ b/sim/libmbit.ts
@@ -322,6 +322,8 @@ namespace ks.rt.micro_bit {
     
     export function setAnalogPeriodUs(pin: Pin, micros:number) {
         pin.mode = PinMode.Analog | PinMode.Output;
+        pin.period = micros;
+        board().updateView();
     }
     
     export function servoWritePin(pin: Pin, value: number) {
@@ -385,16 +387,33 @@ namespace ks.rt.micro_bit {
     }
     
     export function enablePitch(pin: Pin) {
-        pin.mode = PinMode.Analog | PinMode.Output;
+        pin.mode = PinMode.Analog | PinMode.Output | PinMode.Pitch;
     }
     
     export function pitch(frequency: number, ms: number) {
+        // update analog output
+        let pin = board().pins.filter(pin => !!pin && (pin.mode & PinMode.Pitch) != 0)[0] || board().pins[0];
+        if (frequency <= 0) {
+            pin.value = 0;     
+            pin.period = 0;       
+        } else {
+            pin.value = 512;
+            pin.period = 1000000/frequency;        
+        }
+        board().updateView();
+        
         let cb = getResume();
         AudioContextManager.tone(frequency, 1);
-        setTimeout(() => {
-            if (ms > 0) AudioContextManager.stop();            
-            cb() 
-        }, ms);
+        if (ms <= 0) cb();
+        else {
+            setTimeout(() => {
+                AudioContextManager.stop();            
+                pin.value = 0;   
+                pin.period = 0;     
+                board().updateView();
+                cb() 
+            }, ms);
+        }
     }
     
     
diff --git a/sim/simsvg.ts b/sim/simsvg.ts
index 9f3158be..2bf687fd 100644
--- a/sim/simsvg.ts
+++ b/sim/simsvg.ts
@@ -219,7 +219,7 @@ namespace ks.rt.micro_bit {
             let v = '';
             if (pin.mode & PinMode.Analog) {
                 v = Math.floor(100 - (pin.value || 0) / 1023 * 100) + '%';
-                if(text) text.textContent = (pin.value || 0) + "";
+                if(text) text.textContent = (pin.period ? "~" : "") + (pin.value || 0) + "";
             }
             else if (pin.mode & PinMode.Digital) {
                 v = pin.value > 0 ? '0%' : '100%';
diff --git a/sim/state.ts b/sim/state.ts
index 104a3748..abbf7778 100644
--- a/sim/state.ts
+++ b/sim/state.ts
@@ -14,13 +14,15 @@ namespace ks.rt.micro_bit {
         Analog = 0x0002,
         Input = 0x0004,
         Output = 0x0008,
-        Touch = 0x0010
+        Touch = 0x0010,
+        Pitch = 0x0020
     }
 
     export class Pin {
         constructor(public id: number) { }
         touched = false;
         value = 0;
+        period = 0;
         mode = PinMode.Unused;
 
         isTouched(): boolean {