  We show that the multicomponent meson systems can be described by chiral
perturbation theory. We chiefly focus on a system of two pion gases at
different isospin chemical potential, deriving the general expression of the
chiral Lagrangian, the ground state properties and the spectrum of the
low-energy excitations. We consider two different kinds of interactions between
the two meson gases: one which does not lock the two chiral symmetry groups and
one which does lock them. The former is a kind of interaction that has already
been discussed in mutlicomponent superfluids. The latter is perhaps more
interesting, because seems to be related to an instability. Although the
pressure of the system does not show any instability, we find that for
sufficiently strong locking, the spectrum of one Bogolyubov mode becomes
tachyonic. This unstable branch seems to indicate a transition to an
inhomogeneous phase.
