  It is possible to show that there are three independent families of models
describing a massive spin-2 particle via a rank-2 tensor. One of them contains
the massive Fierz-Pauli model, the only case described by a symmetric tensor.
The three families have different local symmetries in the massless limit and
can not be interconnected by any local field redefinition. We show here
however, that they can be related with the help of a decoupled and non dynamic
(spectator) field. The spectator field may be either an antisymmetric tensor
$B_{\mu\nu}=-B_{\nu\mu}$, a vector $A_{\mu}$ or a scalar field $\varphi$,
corresponding to each of the three families. The addition of the extra field
allows us to formulate master actions which interpolate between the symmetric
Fierz-Pauli theory and the other models. We argue that massive gravity models
based on the Fierz-Pauli theory are not expected to be equivalent to possible
local self-interacting theories built up on the top of the two new families of
massive spin-2 models.
  The approach used here may be useful to investigate dual (nonsymmetric)
formulations of higher spin particles.
