One of the fundamental thoughts behind this composition is expressed in the actual invention of the sound-sources: new instruments as self-evident supplements to currently existent sound-makers (together with experimental acoustical equipment, the manipulation of which presupposes a diverse musical faculty).
The work consists of two, almost separate, plains; one constitutes the playback of a 4-track tape recorder with a fixed sequence, whereas the second derives from the playing of 2 to 5 musicians which can be varied from performance to performance in the construction of acoustic material and in the manner of interreaction. I have deliberately avoided combining both plains as I have always had the impression (also in my works which display similar problems) that the attempt to weld together electronic and instrumental music is more wishful thinking on the part of the listener than acoustical reality. (On the other hand, this blending is immediately attainable if the total sound comes from the loudspeaker).
The four-track tape was produced in winter of 1969 in the electronic music studio of West German Radio, Cologne (WDR). The recording consists of purely electroacoustically produced material as well as recordings of instrumental and vocal sounds. The voices of Alfred Feussner and William Pearson are also to be heard in the tape part.
The point of departure for this tape-composition was to compound, as homogeneously as possible, two categories of sounds, dissimilar in the nature of their production (a combination which seemed to me over-simplified when produced by means of a metamorphosis of the concrete recordings by filtering, ring modulation and alteration of the tape playback). It should rather be achieved by similar treatment of instruments and electronic sound-production.
The original instrumental part of the work was written on approximately 200 filing-cards, in the top right-hand corner of which the relevant main-instrument is indicated by a symbol. Neither the order of the cards nor the manner of ensemble is specified, every action is, however, exactly predetermined. The performers always decide the point of their entries; this freedom demands, however, a perfect mastery of text and context. Thus the performers achieve more than a mere reproduction of their parts, as they incorporate influences from one another in their playing as if they were their own audience.
Acustica is written in memory of Alfred Feussner, my early-departed friend. (Mauricio Kagel)
Acustica is perhaps the most refined example of Kagel's work within his invented genre of 'instrumental theatre'. The score notes that 'the piece calls for unorthodox musicians who are prepared to extend the frontiers of their craft' since few of the 'experimental sound devices' specified are conventional instruments and where conventional instruments are included they are to be played in extraordinary ways. Each instrumental action is, however, meticulously notated and the creation and/or modification of instruments are also shown in diagrams and photographs. What the score does not specify is the order in which the individual instrumental events are to be played; Kagel suggests instead that each performer should select the events that they want to perform and then discover in rehearsal how best to order them in combination both with the pre-recorded material and with the sounds of the other players. If the result owes obvious debts both to John Cage and to the theatre of the absurd, its subversive critique of received ideas on what constitutes music and musical instruments is above all typical of Kagel, contemporary master of irony. (Christopher Fox)