  The main goal of this paper is to give a modular type representation for the
infinite product $(1-x)(1-xq)(1-xq^2)(1-xq^3)...$. It is shown that this
representation essentially contains the well-known modular formulae either for
Dedekind's eta function, Jacobi theta function or for certain Lambert series.
Thus a new and unified approach is outlined for the study of elliptic and
modular functions and related series.
