The Lipari-Szabo dynamical formalism is extended by setting the time c
onstants of the Lorentzian terms to -1/omega(N) and 1/(omega(H) + omeg
a(N)). This analysis is compared to the earlier proposed three-paramet
er (S-f(2),S-s(2),tau(s)) extended model free formalism with regard to
the range of equivalence and the advantages of the simplified two-par
ameter (S-f(2),S-H(2)) and (S-f(2),S-N(2)) representations. Spectral d
ensity components are calculated and compared to those obtained from t
he spectral density analysis formalism. Protein relaxation data, commo
nly analyzed in terms of the two-parameter (S-2,tau(e)) representation
, may correspond to a dynamically heterogeneous behaviour that is more
appropriately represented in terms of a fast limit order parameter an
d a second, lower frequency order parameter.