  Even though matrix model partition functions do not exhaust the entire set of
tau-functions relevant for string theory, they seem to be elementary building
blocks for many others and they seem to properly capture the fundamental
symplicial nature of quantum gravity and string theory. We propose to consider
matrix model partition functions as new special functions. This means they
should be investigated and put into some standard form, with no reference to
particular applications. At the same time, the tables and lists of properties
should be full enough to avoid discoveries of unexpected peculiarities in new
applications. This is a big job, and the present paper is just a step in this
direction. Here we restrict our consideration to the finite-size Hermitean
1-matrix model and concentrate mostly on its phase/branch structure arising
when the partition function is considered as a D-module. We discuss the role of
the CIV-DV prepotential (as generating a possible basis in the linear space of
solutions to the Virasoro constraints, but with a lack of understanding of why
and how this basis is distinguished) and evaluate first few multiloop
correlators, which generalize semicircular distribution to the case of
multitrace and non-planar correlators.
