Not heard 'Temi Descrittivi Per Piccolo Complesso' yet. I shall investigate.
Although, a soundtrack and not a library record, for me my favourite is La ragazza fuori strada, although there are several cues and alternative versions from this that also feature on his double library LP, Piero Umiliani E La Sua Orchestra – Gli Archi Raccontano..... (Liuto) which is still pretty cheap to pick up an original and one of a few of his releases that has still not been reissued.
