  We discuss a realization of the non-abelian group O(2) as a family symmetry
for the lepton sector. The reflection contained in O(2) acts as a mu-tau
interchange symmetry, enforcing--at tree level--maximal atmospheric neutrino
mixing and a vanishing mixing angle theta_13. The small ratio m_mu/m_tau (muon
over tau mass) gives rise to a suppression factor in the mass of one of the
pseudoscalars of the model. We argue that such a light pseudoscalar does not
violate any experimental constraint.
