Radio art or radioart is a new genre of art and I think this is the most advanced genre among the arts using electronics. The first international festival of "radio art" was held in Dublin, Ireland, August 12 to 18, 1990 . At the time, however, radio art was mostly considered as an art using the existing radio station that consisted of regular transmission facilities. The difference would be in the contents and the audio facilities. In short, radio art was mere a new family member of radio programs. This would not be impolite to the numerous admirable works of sounds and music using radio station. I am talking about what the concept of radio art or radioart is or should be. As long as we use this term, it should express something newer than the existing genre. In order to rethink on this point, let’s use "radioart" rather than "radio art" from now on.
What is radioart? Who is radioart ? Popular meaning of "radio" has been a receiving tool of radio signals. There is and can be radioart using such a tool. More positively, radioart would be involved in wireless transmission. However, such a transmission remains in the function of broadcasting. Radio station broadcasts. Broadcast means 'cast broadly'. Sometimes broadcasting is done not so broadly. It is called "narrowcasting". But it still does cast. Broadcasting has been seeking for more and more broader range of transmission toward nation-wide, worldwide and space-wide (satellite) broadcasting.
Broadcasting presumes the dualistic two elements: sender and receiver or transmitting and receiving. These two elements must be in accordance by tuning of the input and the output. In this accordance, they say that messages are delivered from one point to another. Broadcasting is considered as a point-to-point relationship. Broadcasting has been seeking to expand the distance between such points as far as possible. The development of recent electronic technology has been easily enabling to expand the distance. Digital broadcasting is supposed to perfectly enable such an accordance of the input of and output. However, difference between the input and the output never disappears unless extreme and forced abstraction or simplification is introduced. One of the most obvious examples of such an enforcement and abstraction would be Morse code communication. Even this simplified communication has to rely on the process of interpretation of the signals. As long as a person operates sending and receiving, arbitrary and redundancy would intervene in the communication. In this sense, radio has been seized with a modernist paranoia of accordance of I/O by tuning. Digital technology is expected to satisfy such a paranoiac dream .
The Internet already sketches what very different things are happening in the contemporary electronic medium. Potentially, the Internet erases the difference between the sender and the receiver. It proves that the set concept of "sender" and "receiver" is obsolete. It should be relevant to think about radio transmission from the perspective of computer. In fact, computer is a transmitter. This transmitter does not deliver anything. Computer does not deliver messages but can duplicate everything omnipresent. You could say that a message is virtually delivered from one place to another. But the fact is that duplication appears in different places. Computer does not expand messages from one place to another but operates sampling locally and can proliferate it globally. I called this function as "translocal". Different from "global medium" such as satellite broadcasting to cover global zone with homogeneous contents, the Internet can infinitely multiply local units and simultaneously can duplicate them remotely. Computer creates polymorphous space where different unit of semiological sings relate each other and interwoven.
I was involved in Mini FM that means a miniaturized FM radio station that was very popular in the 80s in Japan . From the early 80s to the mid 80s, hundreds of stations appeared across the country. Before the new name of "Mini FM", we called our activity as "free radio" deeply influenced by the Italian free radio scene in the late 70s. Among various types of stations, we started our Mini FM "Radio Home Run " as a narrowcasting for local communities or venues where artists and activists got together. "Radio Home Run" connotes "over the border". While being involved in Mini FM, I found that a certain limitation of service area created a new communication. It was amazing that a walking distance radio was not a childish attempt but provided different form of communication: the station was not only a transmitting place but also a totally unconventional space for artists, activists, students and bohemians. The program might have been poor and ill-organized, but the space revitalized new emotion of the participants. Meanwhile I became familiar with Félix Guattari's concepts  of "micro politics" and "molecular revolution" , and was able to make sure that Mini FM unconsciously stepped into such dimensions. In my understanding of Guattari-Deleuze, "molecular" is the minimum unit of singularity and multiplicity. Unless you don't change this level, any thing will be changed at all. In 1985, Guattari came to Japan  and visited Radio Home Run. He recognized that our attempt was seeking a kind of his "molecular revolution" and "Schizoanalysis" in his idiosyncratic term. I became aware that Mini FM could reveal every details and trivia of what we are thinking and feeling.
In 1995, I started my website called "Polymorphous Space" that has a subtitle of "Translocal Weaving Connections ". My experience with the Internet made sure that the authentic function of transmitter (computer) is not to cast but to vitalize and the transmitting size of "local or global" is not so important. Every local unit of transmission is translocal and it contains something global in it. This is quite natural in the area of organic cells from the perspective of molecular biology.
Now we can say that Mini FM was a transitional form from broadcasting radio to something to overcome it. One of the new things is that the action of transmission itself can be considered as a collective performance art. Also, Mini FM let me find that in radio the point is not the type of contents but the size of transmission. And then I became interested in how far minimized the size is. Finally I have arrived at a notion that a hand size of radio transmission could be possible. I insist "hands" because hands are the minimal unit of our body as long as they have the dual functions: touching and being touched. Also, the concept of art derives from techne in old Greek and meant 'hand-work'. Therefore I can say that a minimal Mini FM could be a modest model of radio art.
The concept of "radio art" is quite old. Since the Futurists' interest in radio in the thirties, many artists and theoreticians have been involved in radio from the perspective of art. However, as I mentioned, most of them relied on already existed radio (broadcasting) stations. The point was contents that the stations carried. It was "art radio" instead of "radio art". They considered radio as a medium just like paper for book. Radio technology was secondary. John Cage was one of the earliest artists who used radio technology for creating his new sound pieces and his performance art. But even Cage used radio as a tool for music and sound art. Instead of historic and scholastic consideration of "radio art", I would like to thrust into examining the concept itself.
When does radio become into radioart beyond being a medium? For newspaper, for instance, paper is a medium. So plastic and liquid crystal display (LCD) can be substituted for it. How and when paper becomes an art? It is when the material of "paper" changes itself into a different material. Whatever you write and draw on a sheet of paper, it remains a medium. Therefore such attempts create not paperart but art on the paper. And when you crumple up it, it becomes a garbage. Adorno argued that "all post-Auschwitz culture, including its urgent critiques, is garbage" . This "garbage" (Muell) is, however, not a worthless thing but a new material of art in Adorno's critical perspective . In my interpretation, post-modern arts (arts after the modernism) starts with Adorno's "garbage . His argument advocated "trash art". But considering his critiques against the electronic mass medium such as radio and television we can argue that the most post-modern material as "garbage" would be airwaves.
Thinking about how airwaves as garbage become an art, the aforesaid example of paper might help us. When a sheet of paper is crumpled, it becomes garbage and at the same time it has many folds. They damage the material as a writing/drawing paper but change this material into another. Giles Deleuze provides an interesting understanding on fold although it is in relation to Leibniz' monadology.
A labyrinth is said, etymologically, to be multiple because it contains many folds. the multiple is not only what has many parts but also what is folded in many ways. 
This argument is very suggestive because this talks about the difference of multiplicity not by contents of material but by the material itself. Parts create multiplicity of contents, but they do not change the material itself. They are only a parasite on the material. In the example of airwaves, contents/parts are parasites on the airwaves: that's why broadcasting airwaves are called "carrier".
Radioart has started with intervening directly in the material called "airwaves". They are classified from different and various waves to which airwaves belong. These waves are sometimes audible and visible and sometimes inaudible and invisible. Conventionally, airwaves are classified as EHF, SHF, UHF, VHF, HF, LF, VLF and so on. Whatever frequency is, every airwave radiates. Radio is radiation. Radioart tries to intervene in radiation by electromagnetic transmission and create a certain form of waves. The form of radiation is oscillation. Waves oscillate. When our body and senses can have an appropriate 'resonance', we can perceive the waves. But waves oscillate themselves even without our perception. Waves oscillate by themselves. Waves swing back and forth, up and down, omnidirectionally. Waves themselves don't convey anything. They are a Heraclitean free play of waves: panta rhei.
Radio art is a way to be involved in such an oscillation of airwaves. As long as we don't expect any kind of telepathy or extrasensory perception, we need a detection interface that enables us to perceive as vibrations, sounds, or lights. But these are not the sign of messages but the sign of an "inner life" of waves. In his conversation with Daniel Charles, John Cage said an interesting comment using an example of a ashtray: he said, an ashtray is in state of vibration. But we can't hear those vibration. And in a anechoic chamber, "I'm going to listen to its inner life thanks to a suitable technology, which surely will not have been designed for that purpose." 
After the Mini FM movement was over, along with my attempt to use the Internet radio and with radio party using micro transmitters, my challenge of radioart has been to shrink the size of transmission up to the minimum. How to decide the minimum? Given that I commit myself to transmitting as an artist, a man of techne, i.e. a creating-transforming subject using hands, the minimum size that the airwaves and my body act together should be the distance that I stretch out my hands full-length. That is one-meter radius. I
built a transmitter that can cover one-meter radius and tried to create a kind of folds of airwaves.
Recently, radio landscape (I would prefer to call it as 'radios scape') is popular especially in VLF. You can use it for creating new sound art pieces. But it would be more interesting that you consider it as a play with airwaves. But this "play" means just like what Heidegger wrote about Heraclitus: "Why does it play, the great child of world-play Heraclitus brought into view in the aion? It plays, because it plays."
The sounds would be only an index how you played with airwaves. Radio art is a process art rather than an object art. You cannot fix the live process as it was. In fact, it's very hard to control even one-meter-radius of electromagnetic field. We cannot perfectly control our own hands. Therefore we have to 'release' myself toward things themselves: airwaves themselves.
Regarding the difference of play in my radioart, I can differentiate my performance from sound art, experimental music and noise music. Although it is on the experimental music, Michael Nyman's description would be more appropriate to radioart.
Duchamp once said that the point was to forget with my hand...I wanted to put painting once again at the service of my mind. The head has always been the guiding principle of Western music, and experimental music has successfully taught performers to remember with their hands, to produce and experience sounds physiologically. 
Experimental music has been gradually forgetting "their hands" since digital devices fascinated musicians. The situation of our hands has been drastically changing with appearance of VR technology and robotics. Nobody can deny oneself to be a cyborg one way or the other today. So, horizon between "my hands" and "my mind" has become seamless. But I would like to insist that the point would be to forget with my mind rather than my hands.
 Some of the data can be read and listened in my website: http://anarchy.translocal.jp/radioart/1990IRAF.html
 Weil der Mensch als geschichitlier er selbst ist, muss sich die Frage nach seinem eignen Sein wandeln aus der Form: "Was is der Mensch?" in die Form: "wer ist der Mensch"? , Martin Heidegger, Einfuerung in die Metaphysik,, Max Niemeyer Verlag, 1957, p.110.
 Martin Heidegger deconstructs the Western Metaphysics that the modern science and technology are based on.. He argues that this Metaphysics anticipates such a truth as "the true, whether it be a matter or a proposition, is what accords, the accorcant" [das Wahre, sei es eine wahre Sache oder ein wahre Satz, ist das, whas stimmt, das Stimmende]. (Von Wesen der Waharheit, Vittorio Klostermann, p.7, Pathmarks, Trans. by William McNeill, Cambridge University Press, s138.
 A detailed story is in "Mini FM: Performing Microscopic Distance (An E-Mail Interview with Tetsuo Kogawa", At a Distance Precursors to Art and Activism on the Internet, edited by Annmarie Chandler and Norie Neumark, The MIT Press, 2005, pp.190-209. More theoretical analyses are in my several articles of http://anarchy.translocal.jp/non-japanese/index.html
 Fßlix Guattari, La revolution molßculare, 1977, Edition Recherches,
* The recordings of my three interviews with him are at http://anarchy.translocal.jp/guattari/index.html
 The recordings of my three interviews with him are at http://anarchy.translocal.jp/guattari/index.html
 Alle Kulture nach Auschwitz, samt der dringlichen Kritik daran, ist Muell., Negative Dialectik, suhrkamp taschenbuch wissenshaft 113, 1966, p.359
 Tetsuo Kogawa, "Trash-art in the age of Digital Ash", http://anarchy.translocal.jp/non-japanese/19990808trash-art.html, The Look From the East, MediaArtLab, Moscow, 2000, pp.169-175
Adorno's "Strategy of Hibernation", The Look From the East, MediaArtLab, Moscow, 2000, pp.70-77.
 Gilles Deleuze, The Fold Leibniz and the Baroque, Trans. by Tom Conley, University of Minnesota Press, 1993, p.3.
 John Cage, For the Birds, Marion Boyars, 1976, 1995, pp. 220-221.
 Martin Heidegger, Der Satz vom Grund, Guenther Neske, p.188 [Warum spielt das von Heraklit im aion erblickte grosse Kind des Weltspieles? Es spielt, weil es spielt. Das "Weil" versinkt im Spiel. DasSpiel is ohne "Warum". Es spielt, dieweil es spielt., Trans. by Reginald Lilly, The Principle of Reason, Indiana University Press, p113.
 Michael Nyman, Experimental Music Cage and Beyond, Second Edition, Cambridge, 1999, p.14.
*This article is based on my lecture-performances at AV Festival 2008 in Newcastle, England and Deep Wireless Festival of Radio & Transmission Art in Troronto, Canada. I would like to express my appreciation for Honor Harger, Darren Copeland and Nadene Thßriault-Copeland for giving me a chance to rethink about radioart. The text first appered in Acoustic.Space nr. 7: SPECTROPIA illuminating investigations in the electromagnetic specrum, 2008, Riga, Liepaja, pp.128-135.