  Within the random phase approximation to the spin-Peierls transition two
parameter regimes of phonon softening and hardening are present.
Magneto-elastic excitations are discussed in detail for phonons coupled to the
exactly solvable model of XY spin chains for both regimes, leading to a
modified interpretation of the 30 cm$^{-1}$ mode in CuGeO$_3$. Frustrated
Heisenberg chains coupled to phonons satisfactory describe the pre-transitional
quasi-elastic scattering in CuGeO$_3$. A real space interpretation of the
quasi-elastic scattering is given justifying effective Ising model approaches.
