  We report on a recent investigation on heavy quarkonium hybrids that goes
beyond the usual Born-Oppenheimer approximation by including not only the
mixing between nearby hybrid states but also the mixing with quarkonium states.
We use a systematic effective field theory framework based on NRQCD together
with lattice QCD inputs. Short and long distance constraints from weak coupling
pNRQCD and the QCD effective string theory are also employed. We calculate the
quarkonium and hybrid spectrum for charmonium and bottomonium, and estimate a
number of decay widths. Most of the isospin zero $XYZ$ resonances fit in our
spectrum either as quarkonia or as hybrid states. The mixing of hybrid states
with quarkonia produces enhanced spin symmetry violations, which are
instrumental to understand certain decays. We also present new results on the
hyperfine splittings.
