Melody events (#391)

* support for custom playTone

* added music.onEvent, music.setPlayTone

* updated docs

* updated sample

docs/reference/music/set-play-tone.md

@@ -0,0 +1,38 @@
+# Set Play Tone
+
+Replaces the implementation of the [music play tone](/reference/music/play-tone).
+
+
+```sig
+music.setPlayTone((freq, ms) => {})
+```
+
+### Parameters
+
+* ``f`` the replacement function
+
+### Example
+
+This example send the frequency and duration over radio 
+and plays it on the remote @boardname@.
+
+```typescript
+input.onButtonPressed(Button.A, () => {
+    music.playTone(440, 120)
+    led.toggle(0, 0)
+})
+radio.onDataPacketReceived( ({ receivedNumber }) =>  {
+    const freq = receivedNumber >> 16;
+    const duration = receivedNumber & 0xffff;
+    music.playTone(freq, duration);
+})
+input.onButtonPressed(Button.B, () => {
+    music.setPlayTone((frequency: number, duration: number) => {
+        radio.sendNumber((frequency << 16) | (duration & 0xffff));
+    })    
+})
+```
+### See also
+
+[rest](/reference/music/rest), [ring tone](/reference/music/ring-tone) , [tempo](/reference/music/tempo), [set tempo](/reference/music/set-tempo), 
+[change tempo by](/reference/music/change-tempo-by)