Musicologist Daniel Chua makes a case on his book Absolute Music and the Construction of Meaning for the entwined nature of the birth of the opera and the development of stage machinery.
The use of scenes “in perspective”, as were for the first time deployed in Florentine opera, is part of what Chua accounts for as the conditions for a listening stance: “cosmic infinity has been replaced by the infinity of the vanishing point which puts the human eye at the centre of perception. With this monocular vision, music no longer looks down upon humanity but is looked upon as an object […] what is extended through the eye of the prince beyond the backdrop is the stage machinery” (p. 45-46). This is a “seminal” practice that “created the epistemological structures in which music could be objectified on stage for the perspectival gaze of the subject.”
On the articulation of opera and stage design, he elaborates:
How does this optic regime work? There are two stages to the process: a backstage and a frontstage. The backstage was cluttered with machines. The rituals of magic that imitate the invisible forces of the supernatural world through the descent of deities from clouds and the flying of furies from the pit of hell were controlled with an Oz-like wizardry from behind the scenes. […] The backstage is therefore the site of modern science; the ancient magic that the Camerata sought is only possible through modern technology. For all its magic, opera is a machine world of cause (backstage) and effect (frontstage). So upstage there might be an ancient cosmos with rotating spheres and ethereal beings in full flight, but the magic is thoroughly modern, purely instrumental and entirely human. 1
In Chua’s book this argument is coupled to another fundamental one: that the emergence of a notion of absolute music was inherent in the conditions prompted by the new-born opera. Fundamentally, Chua lays the ground to consider how opera’s staging paradigm informed the kind of attention that symphonic music would later rely upon. In opera the role of text in monody “makes audible the disembodied bubble of the ‘invisible interior’ that is the modern subject; it negates the ‘scriptive space’ of resemblances [that informed the space of music in ancient times, and replaces it with] the sung speech of self-representation” (p. 35).
From Absolute Music and the Construction of Meaning Page 59 (D. Chua)
Gabriel Paiuk (2021): Sound Theory (The Clouds)