  We report a comprehensive study of the tuning with electric fields of the
resonant magneto-exciton optical phonon coupling in gated graphene. For
magnetic fields around $B \sim 25$ T which correspond to the range of the
fundamental magneto-phonon resonance, the electron-phonon coupling can be
switched on and off by tuning the position of the Fermi level in order to Pauli
block the two fundamental inter Landau level excitations. The effects of such a
profound change in the electronic excitation spectrum are traced through
investigations of the optical phonon response in polarization resolved
magneto-Raman scattering experiments. We report on the observation of a
splitting of the phonon feature with satellite peaks developing, at particular
values of the Landau level filling factor, on the low or on the high energy
side of the phonon, depending on the relative energy of the discrete electronic
excitation and of the optical phonon. Shifts of the phonon energy as large as
$\pm60$ cm$^{-1}$ are observed close to the resonance. The intraband electronic
excitation, the cyclotron resonance, is shown to play a relevant role in the
observed spectral evolution of the phonon response.
