  This paper discusses spectral synthesis for those modulation spaces
$M^{p,q}_s({\mathbf R}^n)$ which form Banach algebras under pointwise
multiplication. An important argument will be the ``ideal theory for Segal
algebras'' by H. Reiter [15]. This paper is a continuation of our paper [5]
where the case $q=1$ is treated. As a by-product we obtain a variant of
Wiener-L\'evy theorem for $M^{p,q}_s({\mathbf R}^n)$ and Fourier-Wermer
algebras ${\mathcal F}L^q_s({\mathbf R}^n)$.
