  A new tool for the Evolutionary Synthesis of Stellar Populations (EPS) is
presented, which is based on three independent matrices, giving respectively:
1) the fuel consumption during each evolutionary phase as a function of stellar
mass; 2) the typical temperatures and gravities during such phases; 3) colours
and bolometric corrections as functions of gravity and temperature. The modular
structure of the code allows to easily assess the impact on the synthetic
spectral energy distribution of the various assumptions and model ingredients,
such as, for example, uncertainties in stellar evolutionary models, mixing
length, the temperature distribution of horizontal branch (HB) stars, AGB mass
loss, and colour-temperature transformations. The so-called ``AGB-Phase
Transition'' in Magellanic Cloud clusters is used to calibrate the contribution
of the Thermally Pulsing Asymptotic Giant Branch phase (TP-AGB) to the
synthetic integrated luminosity. As an illustrative example, solar metallicity
($Y=0.27,Z=0.02$) models, with ages ranging between 30 {\rm Myr} and 15 {\rm
Gyr} and various choices for the slope of the Initial Mass Function (IMF), are
presented. Synthetic broad band colours and the luminosity contributions of the
various evolutionary stages are compared with LMC and Galactic globular cluster
data. In all these cases, a good agreement is found. Finally, we show the
evolution of stellar mass-to-light ratios in the bolometric and U,B,V,R, and K
passbands, in which the contribution of stellar remnants is accounted for.
