The magnetic response and the behavior of the harmonic components of a bulk sample of the superconducting composite system YBa2Cu3O7-:Ag0.1 are studied in the presence of a varying sinusoidal magnetic field. It is observed that as the amplitude of the field increases, the wave form of the magnetization M changes from a nearly sinusoidal, to a square-wave-like, then to a two-peak structure, consistent with the prediction of critical-state models. The crossover from the Bean to Anderson-Kim regime is found in the amplitude dependence of the third- and fifth-harmonic response at a fixed temperature. The third-harmonic response shows a peak below Tc as the sample is cooled and the peak shifts to lower temperature and broadens with increasing amplitude of the exciting field. The second-harmonic response, which is zero in the absence of a dc field, passes through a maximum as the dc field is increased. The results of these measurements are in agreement with predictions of the modified critical-state model that incorporates the field dependence of the critical current. © 1992 The American Physical Society.