  We present a systematic study of spin and lattice dynamics in the
quasi-one-dimensional spiral magnet CuBr2, using Raman scattering in
conjunction with infrared and neutron spectroscopy. Along with the development
of spin correlations upon cooling, we observe a rich set of broad Raman bands
at energies that correspond to phonon-dispersion energies near the
one-dimensional magnetic wave vector. The low-energy bands further exhibit a
distinct intensity maximum at the spiral magnetic ordering temperature. We
attribute these unusual observations to two possible underlying mechanisms: (1)
formation of hybrid spin-lattice excitations, and/or (2) "quadrumerization" of
the lattice caused by spin-singlet entanglement in competition with the spiral
magnetism.
