there is an essential difference between the two alternative ground states chosen here as the configurations on top of which the $T\neq 0$ and $\mu\neq 0$ effects are studied: Case (a) corresponds to the standard picture of the NJL hadronic vacuum. In this picture chiral symmetry is spontaneously broken at $T=\mu =0$ when $G>G_{crit}$. Case (b) corresponds to a new alternative, related to the pattern where $G<G_{crit}$. In this case chiral symmetry can be broken only due to the six-quark interactions, when $|\kappa |$ exceeds some critical value (the $8q$-interactions could in principle also induce symmetry breaking, however the mass spectra are then not well reproduced). One can hardly distinguish between the two cases at $T=\mu=0$, the spectra of $0^{-+}$ and $0^{++}$ low-lying mesons do not show much difference: the model parameters are the same, except for the correlated $G$ and $g_1$ values. The larger value of $g_1$ in the case (b) is a signal of the increasing role played by the eight-quark OZI-violating interactions, but this does not affect the value of the mixing angle $\theta_p$, and only slightly diminishes $\theta_s$. Such insensitivity follows from the observation that the stationary phase equations (\[SPA\]) and mass formulae of the light 