  We present singlet-Majoron couplings to Standard Model particles through two
loops at leading order in the seesaw expansion, including couplings to gauge
bosons as well as flavor-changing quark interactions. We discuss and compare
the relevant phenomenological constraints on Majoron production as well as
decaying Majoron dark matter. A comparison with standard seesaw observables in
low-scale settings highlights the importance of searches for
lepton-flavor-violating two-body decays $\ell \to \ell' +$Majoron in both the
muon and tau sectors.
