Gottfried Michael Koenig’s reader Voltage Control: Diagrams and Circuitry (1974) is now available for download. The PDF and the sound examples mentioned in the reader can be found here.
From the introduction:
“This summary contains no information about how studio apparatus is built or how it works, and there are no recipes for sound production. The aim is a more or less systematic survey of the available apparatus and some possibilities of its application.
There are two chief tendencies in the development of electronic studios:
(a) the tendency towards the “construction kit” system: one special piece of apparatus is built for each function: complex functions can be obtained by connecting individual pieces of apparatus (e.g. Utrecht):
(b) the tendency towards the electronic music instrument: each individual piece of apparatus serves a complex purpose: the electronic music instrument thus represents a premeditated selection of all conceivable complex functions (e.g. synthesizer).
This summary will be limited to the first of these tendencies.”