[en] In the framework of a unified theory of direct and resonant reactions the excitation of ⁴⁰Ca by medium-energy projectiles has been investigated. The applied 1p-1h approximation turns out to be capable of describing the gross features of the measured spectra. A considerable part of the smooth background is found to be produced by resonance transitions. A dominant g/sub 9/2/(1d/sub 5/2/)^-1 structure of the giant quadrupole resonance is proposed, which is in agreement with the observed decay channels. The importance of high-lying single-particle states with large angular momentum 1 > 3 is emphasized, in particular for reactions with hadrons. It is shown that coincidence experiments are suitable for suppressing the background. (author)