on a piano there are white and black notes (confusingly these are also called “keys”). the white notes are named by the letters a to g of the alphabet. after g comes another a and so on. the black notes go in threes and twos. this makes it easy to see the pattern of white notes. where there are two black notes together, for example, the white note between them is d. the black notes do not have names of their own. they are named after the white notes next to them. the black note just above (i.e. to the right) of a g is a g sharp. the black note just below (i.e. to the left) of the g is g flat. this means that each black note has two possible names (e.g. g flat or f sharp).