Aural Spectacle
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”, deployed for the first time as part of Florentine opera, is one of the elements that Chua accounts for as the conditions for producing a listening stance: “cosmic infinity has been replaced by the infinity of the vanishing point which puts the human eye at the centre of perception.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 practice “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, 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. […] 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
Chua argues that the emergence of a notion of absolute music was inherent in the conditions created by the new-born opera. The practice of staging that opera inaguturated informed the kind of attention that symphonic music would later on rely upon. In opera the role of text in monody “makes audible the disembodied bubble of the ‘invisible interior’ that is the modern subject” (p. 35).

From Absolute Music and the Construction of Meaning Page 59 (D. Chua)
Gabriel Paiuk (2021): Sound Theory (The Clouds)