  Strongly interacting phonons and orbital excitations are observed in the same
energy range for CuSb$_2$O$_6$, unlocking a so-far unexplored type of
electron-phonon interaction. An orbital wave at $\sim 550$ cm$^{-1}$ softens on
warming and strongly interferes with a phonon at $\sim 500$ cm$^{-1}$, giving
rise to a merged excitation of mixed character. An electronic continuum grows
on warming to the orbital ordering temperature $T_{OO}$=400 K, generating an
important phonon decay channel. This direct and simultaneous observation of
orbital and vibrational excitations reveals details of their combined dynamics.
In addition, phonon frequency anomalies due to magnetic correlations are
observed below $\sim 150$ K, much above the three-dimensional magnetic ordering
temperature $T_N^{3D}=8.5$ K, confirming one-dimensional magnetic correlations
along Cu-O-O-Cu linear chains in the paramagnetic state.
