  The main result of the paper is a description of conormal Lie algebras of
Feigin-Odesskii Poisson structures. In order to obtain it we introduce a new
variant of a definition of a Feigin-Odesskii Poisson structure: we define it
using a differential on the second page of a certain spectral sequence. In the
general case this spectral sequence computes morphisms and higher Ext's between
filtered objects in an abelian category. Moreover, we use our definition to
give another proof of the description of symplectic leaves of Feigin-Odesskii
Poisson structures.
