  The evolution of a relativistic heavy-ion collision is typically understood
as a process that transmutes the initial geometry of the system into the final
momentum distribution of observed hadrons, which can be described via a
cumulant expansion of the initial distribution of energy density and is
represented at leading order as the well-known eccentricity scaling of
anisotropic flow. We summarize a proposed extension of this framework to
include the contribution from initial momentum-space properties, as encoded in
other components of the energy-momentum tensor. Numerical tests validate this
proposal.
