Playing the sequence "GHkLkHGHkLkHGHkLkHGHkLkHfHkLkHfHkLkHfHkLkHfHkLkHfGjkjGfGjkjGfGjkjGfGjkjGfDfGHGfDfGHGfDfGHGfDfGHGf" on a piano keyboard would produce a specific melody or musical pattern. However, without any further information or notations, it is not possible to determine the exact notes and chords to be played.
