Are there some or many songs by Georges Brassens which could be considered as existentialist?
A Wikipedia definition of the philosophy of existentialism (developed by authors such as Kierkegaard, Nietzsche, but also Sartre and Camus):
Existentialism is a form of philosophical inquiry that explores the issue of human existence.1 Existentialist philosophers explore questions related to the meaning, purpose, and value of human existence. Common concepts in existentialist thought include existential crisis, dread, and anxiety in the face of an absurd world, as well as authenticity, courage, and virtue.[3]
I think we can legitimately ask this question, since French existentialism was popular in intellectual circles in Paris, at the moment Brassens lived there (around year 1945) [1], and was politically, professionnally (as a journalist for an anarchist journal) and artistically active.
Thinking about it, many of his lyrics are written from a very subjective standpoint ("Le Parapluie", "Je Me Suis Fait Tout Petit"), and exhibit a quite cynical view on human existence ("Les amoureux des bancs publics", "Il n'y a pas d'amour heureux"), although they don't overtly talk about the absurd.
Edit: Thanks to Armand's answer, I came to the idea that Brassens was certainly in the "cynicism" tradition (Diogenes), therefore his natural acquaintance whith anarchism. This confers him a common point with the hippie movement, which also partly draw upon cynicism.
Definition of cynicism, from the IEP:
Foremost for understanding the Cynic conception of ethics is that virtue is a life lived in accord with nature. Nature offers the clearest indication of how to live the good life, which is characterized by reason, self-sufficiency, and freedom. Social conventions, however, can hinder the good life by compromising freedom and setting up a code of conduct that is opposed to nature and reason. Conventions are not inherently bad; however, for the Cynic, conventions are often absurd and worthy of ridicule. (...) Only once one has freed oneself from the strictures that impede an ethical life can one be said to be truly free. As such, the Cynics advocate askēsis, or practice, over theory as the means to free oneself from convention, promote self-sufficiency, and live in accord with nature. Such askēsis leads the Cynic to live in poverty, embrace hardship and toil, and permits the Cynic to speak freely about the silly, and often vicious, way life is lived by his or her contemporaries.