At the Congress of Experimental Music in Brussels, on October 7 1959, Alfredo Lietti gave a report entitled “Evolution of the technical means for electronic music”. In this report he presented with great detail the main equipment of the Studio of the time, as well as the development process that had led to the realization of such equipment. Most of these devices had been designed and crafted by Lietti himself.
These included the famous nine sinusoidal oscillators, constructed between 1955 and 1956. The user interface consisted of two knobs and a display. The bottom-left numbered knob allowed to choose one among six frequency bands, while the one on the right was used to adjust the oscillation frequency between the minimum and the maximum value in a given frequency band. The display was divided into six scales, one per frequency band. Sound generators built by Lietti also included a white noise generator, obtained by amplifying the electronic noise generated by a vacuum tube, and a pulse generator.
Sound processing elements included a bank of six octave filters designed by Lietti, tuned to the frequencies 200-400, 400-800, 800-1600, 1600-3200, 3200-6400, 6400-12800 Hz, and a bank of low/high-pass filters with cut-off frequencies at 280, 560, 1100, 2200, 4500, 6000 Hz (low-pass), and 280, 560, 1100, 4500, 8500, 160 Hz (high-pass). Lietti also constructed an “amplitude selector”, basically a noise gate originally designed to reduce noise in radio broadcasting. Other custom-built sound processing elements included a ring modulator, an amplitude modulator, a dynamic modulator, and a frequency transposer (one of Lietti’s latest creations).
In addition to these unique pieces of equipment, several commercial devices were added later. Moreover, the equipment included measuring instruments (e.g., a cathode tube comparator used to whether the frequencies generated by two oscillators were in harmonic ratio), mixers, tape recorders, and a mixing desk. The set-up of the Studio underwent several changes after the Lietti’s departure. Original and innovative devices, such as those designed by Lietti in the early years, were no longer created, and instead the Studio was gradually equipped with manufactured devices, which partly replaced and complemented those early ones. Significant changes were made in 1968, when the technical equipment was almost completely renovated. As a consequence of these renovations many of the early Lietti’s devices were dismissed and subsequenly lost: the sinusoidal oscillators, the white noise generator, the octave filters, and others.