Dielectric response of incommensurate phases in order-disorder ferroel
ectrics is studied by means of pseudospin formalism. The complex dynam
ical susceptibility is calculated using the Bloch equations which are
solved either by a perturbational approach or by a procedure introduce
d recently by Lovesey et al. We derive formulae for susceptibility as
a function of frequency which display multirelaxational behaviour due
to the coupling of the homogeneous polar soft mode to higher-order (wi
th respect to their wavevectors) modes.