  Longitudinal and transverse sound velocities of Lennard-Jones systems are
calculated at the liquid-solid coexistence using the additivity principle. The
results are shown to agree well with the ``exact'' values obtained from their
relations to excess energy and pressure. Some consequences, in particular, in
the context of the Lindemann's melting rule and Stokes-Einstein relation
between the self-diffusion and viscosity coefficients are discussed. Comparison
with available experimental data on the sound velocities of solid argon at
melting conditions is provided.
