Greek stories
This is a book of philosophy which takes as its concrete subject matter the plays of ancient Greek tragedy. The hero's journey is told through the lens of hubris and fate for the outcome of catharsis, pity, and fear. That archetypal framework is suggested by Nietzsche as a suitable metaphor for the human experience, which makes Greek tragedy a kind of rejection of nihilism. By asserting that the human experience has artistic merit, and by locating that merit in suffering, the human experience can be said to be meaningful. That does not take away from Nietzsche's own understanding of nihilism, but rather, it is a kind of counterpoint analysis of nihilism (to use the subtitle's invocation of music).
Human life
The human life is the broader concept within which the tragic imagery is situated. It is also the imagery from which art and literature historically emerged. The imagery is dual because Nietzsche considers the imagery from two points of view: the individual point of view and the aggregate point of view. By aggregating the total value of human experience into a continental philosophical concept, Nietzsche rediscovers the logical framework for Aristotle's famous essays on tragedy and art. The question of the imagery is whether meaning is real or imagined, and the answer is located in the paradox of catharsis.
Tragedy and art
Art is an imagery in itself in this book because the author treats art generally and specifically. Most of all, he treats art as a response to human experience, and within that dynamic, he finds tragedy as the purest and highest art. The abstract imagery of art elevates tragedy because there is no more obvious attempt to find meaning in suffering than tragic artwork. That art both condemns hubris which maintains the status quo that nihilism would annihilate, while also celebrating all experience as good insofar as it is essentially meaningful.
Meaning and nihilism
The imagery of nihilism is a rejection of the imagery of meaning, but in this book, Nietzsche honors both points of view putting one within the other. Within the objective absurdity of experience, humans have created art and tragedy which adds meaning to their personal experiences of reality, but of course Nietzsche views reality from a much broader perspective than the simple subjective experience of humans which are born and die. He considers reality from an objective point of view coming to celebrate meaninglessness as a kind of transcendence of tragedy.