  We study the thermodynamic properties of matter at vanishing temperature for
non-extreme values of the isospin chemical potential and of the strange quark
chemical potential. From the leading order pressure obtained by maximizing the
static chiral Lagrangian density we derive a simple expression for the equation
of state in the pion condensed phase and in the kaon condensed phase. We find
an analytical expression for the maximum of the ratio between the energy
density and the Stefan-Boltzmann energy density as well as for the isospin
chemical potential at the peak both in good agreement with lattice simulations
of quantum chromodynamics. We speculate on the location of the crossover from
the Bose-Einstein condensate state to the Bardeen-Cooper-Schrieffer state by a
simple analysis of the thermodynamic properties of the system. For $\mu_I
\gtrsim 2 m_\pi$ the leading order chiral perturbation theory breaks down; as
an example it underestimates the energy density of the system and leads to a
wrong asymptotic behavior.
