  We report on the experimental measurement of the dispersion relation of the
density and spin collective excitation modes in an elongated two-component
superfluid of ultracold bosonic atoms. Our parametric spectroscopic technique
is based on the external modulation of the transverse confinement frequency,
leading to the formation of density and spin Faraday waves. We show that the
application of a coherent coupling between the two components reduces the phase
symmetry and gives a finite mass to the spin modes.
