Neutrons are almost never used to examine the role of phonons in materials with large magnetocaloric effects, despite the large magneto-elastic coupling often exhibited by them. We wish to use inelastic (this MARI experiment and one on MERLIN submitted in this round) and elastic neutron scattering (PEARL, proposal submitted) to quantify the change in phonon entropy at the metamagnetic phase transition in CoMnSi, a material relevant to magnetocaloric materials research. In our HRPD studies of this material, we have discovered giant magneto-elastic interactions within the antiferromagnetic state and also that the simple Debye model often used by magnetocaloric materials researchers underestimates the change in phonon entropy. This MARI experiment will make the first ever analysis of the phonon spectrum, to be compared with data gathered on MERLIN on a textured sample in a magnetic field.