Piano music is usually a staff, in which tonality is clearly marked. Therefore, there are generally signs of rising and falling on the staff, indicating that black keys is needed. The song "Wedding in My Dream" is in bB key, which means that all sevens should be dropped by a semitone, that is, black keys to the left of sevens on the keyboard. In the rising and falling symbols, B means flat, and b7 and b3 mean that all 7' s and 3' s in this piece should be flat. Whenever 7 or 3 appears, the left black keys will be used instead of the original white key.

Extended knowledge point: # stands for upward symbol, as opposed to downward symbol.