  We study in this article the concept of algebra up to homotopy for a
structure defined by two operations . Important examples of such structure are
those of pre-Gerstenhaber and pre-Poisson algebras. Given a structure of
pre-commutative and pre-Lie algebra for two shifts of degree given by a and b,
we define the structure of a pre-(a, b)-algebra and we give an explicit
construction of the associated algebra up to homotopy.
