  In this paper we establish a new case of Langlands functoriality. More
precisely, we prove that the tensor product of the compatible system of Galois
representations attached to a level-1 classical modular form and the compatible
system attached to an n-dimensional RACP automorphic representation of GL_n of
the adeles of Q is automorphic, for any positive integer n, under some natural
hypotheses (namely regularity and irreducibility), and a mild restriction on
the level of the n-dimensional representation.
