  We consider the classical elliptic Calogero-Moser model. A set of canonical
separated variables for this model has been constructed in Kuznetsov et al.
However, the generating function of the separating canonical transform is known
only for two- and three-particle cases . We construct this generating function
for the next A_3 case as the limit of the conjectured form of the quantum
separating operator. We show explicitly that this generating function gives a
canonical transform from the set of original variables to the separated ones.
