According to Basilio Franchina, who collaborated on Una voce umana, the encounter between Rossellini and Cocteau was not the work of French critics, who supported both, nor thanks to Paulvé or Josette Day. […] Rather, it was Anna Magnani who brought the two together and helped overcome any reservations. […] Cocteau affirms that: “It is thanks to Paisà, as far as I am concerned, and Le Sang d’un poète, in the case of Rossellini, that we decided to collaborate and to work with Anna Magnani, who is incredible as the only actor in this version of La Voix humaine.” In his on-set correspondence, the journalist Bruno Matarazzo confirms what Cocteau claimed: “After watching Le Sang d’un poète, Rossellini and Cocteau became friends and Rossellini himself asked to make [La Voix humaine], just as the author intended. The latter, who had met Anna Magnani, suddenly realised that he had solved two problems: he had found the perfect director and the perfect actress for his film”. […]
The author did not raise any objections to the changes Rossellini made to the play… “I recall our collaboration as a sort of friendly miracle”. […] Apart from the artistic differences between the pair, this encounter constituted a moment of fundamental change for Rossellini […]. “What I did with [Una voce umana] had never been tried before!. […] More than any other story, Una voce umana gave me the opportunity to use the camera as a microscope, especially since the phenomenon it would be studying was called Anna Magnani. […] This idea, which was pushed to the extreme in Una voce umana, was useful for all the films I made subsequently because at certain points in the filming, I felt the need to set the screenplay aside in order to follow the character’s innermost thoughts, those which perhaps even I was not really aware of. This “microscopic aspect” of the cinema is also a part of neorealism: a moral approach which then becomes an aesthetic one.”

Adriano Aprà, Per un cinema microscopico, in La Voix humaine, “Quaderni della Fondazione Donizetti”, n. 4, 2006