diff --git a/libs/core/_locales/core-strings.json b/libs/core/_locales/core-strings.json
index 33649d06..e0ef32da 100644
--- a/libs/core/_locales/core-strings.json
+++ b/libs/core/_locales/core-strings.json
@@ -94,9 +94,7 @@
   "Rotation.Roll|block": "roll",
   "String.charAt|block": "char from %this=text|at %pos",
   "String.compare|block": "compare %this=text| to %that",
-  "String.concat|block": "join %this=text|%other",
   "String.fromCharCode|block": "text from char code %code",
-  "String.isEmpty|block": "%this=text| is empty",
   "String.length|block": "length of %VALUE",
   "String.substr|block": "substring of %this=text|from %start|of length %length",
   "String|block": "String",
diff --git a/libs/core/music.cpp b/libs/core/music.cpp
index 5154b9b4..b78557bd 100644
--- a/libs/core/music.cpp
+++ b/libs/core/music.cpp
@@ -9,9 +9,13 @@ namespace music {
     //% help=music/play-tone weight=90
     //% blockId=device_play_note block="play|tone %note=device_note|for %duration=device_beat" icon="\uf025" blockGap=8
     //% parts="speaker" async
-    void playTone(int freqency, int ms) {
-        uBit.soundmotor.soundOn(freqency);
-        if(ms > 0) uBit.sleep(ms);
-        uBit.soundmotor.soundOff();
+    void playTone(int frequency, int ms) {
+        if(frequency > 0) uBit.soundmotor.soundOn(frequency);
+        else uBit.soundmotor.soundOff();
+        if(ms > 0) {
+            uBit.sleep(ms);
+            uBit.soundmotor.soundOff();
+        }
+
     }
 }