Added some music documentation (#2198)

src/sound.c

@@ -33,6 +33,7 @@ static void CreateFanfareTask(void);
 static void Task_DuckBGMForPokemonCry(u8 taskId);
 static void RestoreBGMVolumeAfterPokemonCry(void);
 
+// The 1st argument in the table is the length of the fanfare, measured in frames. This is calculated by taking the duration of the midi file, multiplying by 59.72750056960583, and rounding up to the next nearest integer.
 static const struct Fanfare sFanfares[] = {
     [FANFARE_LEVEL_UP]            = { MUS_LEVEL_UP,             80 },
     [FANFARE_OBTAIN_ITEM]         = { MUS_OBTAIN_ITEM,         160 },