In this work a practical method of fitting complex multiphase Mossbauer eff
ect spectra is proposed. The task is simplified imposing specific restricti
ons to the analysing functions, which are appropriate for cases where the c
omponent phases spectra do not change substantially during the process unde
r study. The ME spectra can be analysed using the phases subspectra, by def
ining only a reduced number of parameters. The constraints are equivalent t
o assume a Doppler velocity transformation v' = (v - delta (m))B-m0/B-m + d
elta (m0) for each phase, where delta (m) and B-m are fitting parameters co
ntaining information on the phase mean isomer shift and hyperfine field and
delta (m0) and B-m0 their reference values. In this manner physically mean
ingful results are easy to obtain. The idea was applied to partially nitrog
enated R(2)Fe(17)Nx (R = Sm and Y) and partially hydrogen-decomposed Nd-Fe-
B materials.