Finding your way

A piano has 88 keys and they all look the same. By the end of this you will be able to find any one of them in about a second, without counting from either end.

There are only seven names, and then they start over: C, D, E, F, G, A, B — or dó, ré, mi, fá, sol, lá, si, which is the same seven notes under the other naming system. What is left is where they sit, and that is a question about this instrument and no other.