SPoT stellar population models obtained with non-canonical assumptions. In all cases the initial (standard) population has solar metallicity and t ~ 14 Gyr, and is shown with a blue star in each panel, while the final composite population is shown with a different colour and connected with a dashed line to the reference model. Upper panels show main annulus measures, while middle and lower panels show multi-annuli measures and SNe Ia regions. Left panels: a fraction equal to 50% of the total HB-stars is simulated as HHB. For these models three ages are considered (t = 10, 12, and 14 Gyr increasing ages are marked with larger symbols). Middle panels: a young population of t = 30 Myr (red) or t = 100 Myr (magenta) is added to the old solar one. The fraction in mass of old to young stars is reported in the lower panel. Right panels: various metallicities are added to the solar one, as labelled. The mass fraction metal-poor to standard SSPs is shown in the lower panel. Symbols for observational data are as in Fig. 4 (See electronic version of the Journal for a colour version of the figure).