  We investigated the spin excitations of magnetoelectric $\text{LiFePO}_4$ by
THz absorption spectroscopy in magnetic fields up to 33$\,$T. By studying their
selection rules, we found not only magnetic-dipole, but also electric-dipole
active (electromagnons) and magnetoelectric resonances. The magnetic field
dependence of four strong low-energy modes is reproduced well by our
four-sublattice spin model for fields applied along the three orthorhombic
axes. From the fit, we refined the exchange couplings, single-ion anisotropies,
and the Dzyaloshinskii-Moriya interaction parameters. Additional spin
excitations not described by the mean-field model are observed at higher
frequencies. Some of them shows a strong shift with magnetic field, up to
4$\,\text{cm}^{-1}/\text{T}$, when the field is applied along the easy axis.
Based on this field dependence, we attribute these high frequency resonances to
excitation of higher spin multipoles and of two magnons, which become
THz-active due to the low symmetry of the magnetically ordered state.
