I present an evolutionary stellar population synthesis model which predicts spectral energy distributions, SEDs, for simple old single-metallicity stellar populations, SSPs, in the wavelength intervals λλ 3856-4476Å and 4795-5465Å at a resolution of FWHM$equals;1.8 $Aring;, on the basis of an extensive empirical spectral library composed of ~550 stars. The synthesized model spectra can be used to analyse observed galaxy spectra in a very easy and flexible way, allowing us to adapt the theoretical predictions to the characteristics of the data instead of proceeding in the opposite direction (as we must do,for example, when transforming observational data to a particular system of indices at specific resolution/s, such as Lick, which is heavily instrument-dependent). The SSP spectra, with flux-calibrated response curves, can be smoothed to the same resolution as that of the data or to galaxy internal velocity dispersion, allowing us to analyse the observed spectra in their own system, and with no need to correct the index measurements for velocity dispersion. Thus, we are able to use all the information contained in the data, at their higher spectral resolution. Excellent fits are obtained for various metal-rich globular clusters at relatively high resolution, and well known spectral peculiarities such as the strong CN absorption features are detected. When applied to early-type galaxies the model also shows its potential for studying element ratios such as the Mg/Fe overabundance. The model spectra provided robust age indicators for old stellar populations which do not depend on metallicity and therefore have a great potential for solving the age-metallicity degeneracy of galaxy spectra.