  It is possible to extract, from the observations, distribution functions of
the birth dynamical properties of a stellar population, and to also infer that
these are quite invariant to the physical conditions of star formation. The
most famous example is the stellar IMF, and the initial binary population (IBP)
seems to follow suit. A compact mathematical formulation of the IBP can be
derived from the data. It has three broad parts: the IBP of the dominant
stellar population (0.08-2 M_sol), the IBP of the more-massive stars and the
IBP of brown dwarfs. These three mass regimes correspond to different physical
regimes of star formation but not to structure in the IMF. With this
formulation of the IBP it becomes possible to synthesise the stellar-population
of whole galaxies.
