We will have 3 options which will be toggable.
a. By default, it will be "add" option. The normal way, as it is currently in which we will add the notes. b. On clicking it once, it will change to "replace". Now we can click on any note and then click on the piano key to replace it. c. The final option will be "erase". Now, the user can click on any note and it will be replaced by a rest of the same length.