  The lower part of the classical instability strip and the surrounding main
sequence are populated by a large variety of pulsating variable stars. In the
past years a great effort was made by the stellar group of Brera Observatory to
collect a large amount of photometric and spectroscopic data on Delta Sct
stars, the more numerous class. In this paper I will describe our approach to
this study. In Sect. 2.1 I show as the light curves of high-amplitude Delta Sct
stars can be described in a synthetic and powerful way by using the Fourier
decomposition. In Sect. 2.2 some interesting cases are presented, i.e. the
peculiar light curves of some double-mode pulsators and the multiperiodicity of
V974 Oph. As regards the small amplitude Delta Sct stars, the results which can
be extracted from the photometry and (high-resolution) spectroscopy are
discussed in Sect. 3; the importance of combining the two techniques into the
synergic approach is stressed. As a final step, an excursus on the Gamma Dor
stars is presented in Sect.4; the rich pulsational content makes these stars
very similar to Delta Sct variables.
