  The extensive catalog of waveforms, with details of binary black hole
inspiral and merger, offer an opportunity to understand black hole interactions
beyond the large separation regime. We envision a research program that focuses
on the transfer of angular momentum from spin of the individual holes to the
orbital angular momentum and the role of tidal coupling in the process. That
analysis will require the formulation of an expression for the orbital angular
momentum of a binary, an expression that is useful at small separations, since
that regime is well out of the range of Newtonian approximations and is where
tidal coupling should be most interesting. We report here such an expression, a
binary orbital angular momentum based on numerical relativity results for
quasi-circular orbits, that agrees remarkably well with a similar quantity
constructed with particle-perturbation techniques for the Kerr geometry.
