  In this paper we review some connections between harmonic analysis and the
modern theory of automorphic forms. We indicate in some examples how the study
of problems of harmonic analysis brings us to the important objects of the
theory of automorphic forms, and conversely. We consider classical groups and
their unitary, tempered, automorphic and unramified duals. The most important
representations in our paper are the isolated points in these duals.
