Mauricio Kagel, "Acustica" (Side Three)

...
Balloons as resonators for wind instruments and as (regained) air-supply in the production of oral processes;

Pipe-branch, a piece of narrow hose approx. 130' long with connections (on the ends of which organ pipes [mixtures] and penny-whistles are attached), which is fed by a compressed-air cylinder of 27 cubic feet capacity (an "aerophone" for collective use, where only generously-minded players can play together: should one of the performers divert the air-current for himself alone, all the others will be made silent);

Gas blow-lamp, to produce vibrations in pipes, the fundamental frequency of which is reached by altering its total length;

Mutes for wind instruments with built-in loudspeakers which permit a perfect diaphony with the simultaneous playback from the tape recorder of the blown notes;

Megaphones, likewise with built-in loudspeakers (also to be used by contestants, in which case power-saving cassette-recorders are switched on to drown the puny volume of the official side);

Humming-loudspeaker (the German term "Summenlautsprecher" derives both from "Summe" = sum and from "summen" = to hum), the diaphragm of which is worked on with various articles during the performance (so that the loudspeaker becomes more of an instrument than an actual loudspeaker).