  We present a new method to find solutions of the Virasoro master equations
for any affine Lie algebra $\widehat{g}$. The basic idea is to consider first
the simplified case of an In\"on\"u-Wigner contraction $\widehat{g}_c$ of
$\widehat{g}$ and to extend the Virasoro constructions of $\widehat{g}_c$ to
$\widehat{g}$ by a perturbative expansion in the contraction parameter. The
method is then applied to the orthogonal algebras, leading to fixed-level
multi-parameter Virasoro constructions, which are the generalisations of the
one-parameter Virasoro construction of $\widehat{su}(2)$ at level four.
