Complex sentence: He also recorded Giordano's "Fedora" with Magda Olivero and was a mentor to several noted sopranos, including Lucia Aliberti and Sylvia Sass, with whom he made the recording of "Stiffelio".
Split into simpler sentences: He also recorded Giordano's "Fedora" (with Magda Olivero). Gardelli was also a mentor to several noted sopranos, including Lucia Aliberti and Sylvia Sass, with whom he made the recording of "Stiffelio".