"...[A] void exists between musical acoustics and music properly speaking, that it is necessary to fill this void with a science describing sounds, joined to an art of hearing them, and that this hybrid discipline clearly grounds our musical efforts."
Phenomenology seeks to be this hybrid discipline to fill the void between objectivity (musical acoustics, for example) and subjectivity (music properly speaking). A good musical example of this notion is the difference between frequency and pitch. Frequency is the number of sound waves in a given time; pitch is the way we perceive the frequency. 440 hertz is a frequency; A is the the pitch. Schaeffer's void is the almost ungraspable space between the objective known and the perceived.
It's the space-between that reminds me of counterpoint. Maybe counterpoint is a reflection of the Void, or negative space more generally, and it's the ungraspability of counterpoint that makes it so interesting. Some would argue that it's completely graspable. Indeed, it can be described in great detail. Schenkarian graphs are one example of this description. Species counterpoint captures the essence of a style in order to teach students to emulate that style. But, those examples are akin to the "musical acoustics" of Schaeffer's quotation above. What is less clear is the listener's perception of counterpoint. It's nebulous.