updated docs

docs/reference/music.md

@@ -1,14 +1,13 @@
 # Music
 
-
-
+Generation of music tones through pin ``P0``.
 
 ```cards
 music.playTone(0, 0);
 music.ringTone(0);
 music.rest(0);
 music.noteFrequency(Note.C);
-music.beat();
+music.beat(BeatFraction.Whole);
 music.tempo();
 music.changeTempoBy(20);
 music.setTempo(120);