Electronic technologies have played a decisive role in music since the early years of the twentieth century. Developed as conservative devices for the acoustic information (CD,tape) and for radio broadcasting, they gradually established an active role through the amplification and the processing of the traditional acoustic instruments. With the coming of the computer, technology have actually assumed an irreplaceable role also in the expressive experience of the music. The second half of the twentieth century testified the birth and development of the Electronic Music which has been decisive for the languages transformation ​​but also for the listening, participation and enjoyment of the music transformation criteria; especially among new generations, where the relationship with technology is almost daily, their use has become natural as artistic expression vehicle.
An important aspect which characterizes the high diffusion of technology in music, is represented by the scientific effort given by the private centers and universities all over the world for over fifty years, and through important industrial investments that have extended the audience to professional and amateur use. Scientific research, which has been used by the music, has meant in-depth analysis of some disciplines such as the architectural and instrumental acoustic, psychoacoustics, or ways to perceive and decipher sound information, the analysis, synthesis and recognition of the sound. With computer and software dedicated to music, sophisticated control of the sound conditions have been developed and today allow us to subordinate the machine to the most complex needs of the artistic creativity: from processing and transformation of the orchestra sounds to their accurate diffusion in space, from the synthesis of innovative timbres to the creation of virtual environments where the public interacts.
These experiences have re-established the whole musical system and allow us to access to concepts such as: interactive opera, multimedia or intermedia opera, distributed opera (this is the case of productions and performances between more users realized with the aid of communications by air and by Internet).

Art Sound installation
Musical works which have introduced in Italy the main innovations in the adaptive and interactive field are, without doubt, the Installazioni sonore d’arte (art sound installations) (CRM, 1995). They have deeply transformed the ways of fruition and the access to multimedia and intermedia criteria. Installations of this kind are works able to immerse the listener into an environment which may present a way to consider the space, both physical (distribution of sound sources, visual and plastic elements, paths, etc..) and virtual. They can assume different forms and means of expression according to the spaces they should occupy and the kind of relationship they establish with the user.
The Installazione sonora d’arte [1] is, among the musical work, the one which highlights, more than any other, the innovative features of fruition. The synergy it can established with the user, the environment and the architecture, the materials and the sculptural forms, over the time and through events, enables it to offer to the public a related set of experiences which stimulates the sensitivity for the artistic and expressive sign and stimulates knowledge.
They are innovative musical compositions because they are able to involve the audience active participation; for example, the public has the opportunity to choose the listening condition which suits them most and to enjoy the work while moving along free paths or directed by compositional criteria [2]. The fruition of musical work is achieved through an overall experience of sound and environment; it employs the senses in a correlated way, stimulating first the intuitive level and then the cognitive and active participation of the listener who chooses, for listening, the most congenial condition.
When in these works the “interaction” is provided, this is developed according to stimulus criteria toward creativity. This is the case where the performer or the public actions influence the space-time evolution, through sensors and interfaces for this purpose.
When the work has "adaptive" features, its musical content may present very different patterns of expression, even within few hours; the musical work can theoretically become infinite and give different content according to its history and the current sound, to visual and tactile developments all around. Within this framework the experiences are next to the artificial intelligence applications and represent a frontier of great interest for the art as a whole because they play a deep and conscious critical and cognitive action about the role that technologies have for the human expression and communication.

Interactive, Adaptive and Evolutive
The two systems categories described above represent a remarkable direction of the current scientific and artistic research. The creative use of technology, in art and in all contexts in general, has as its fundamental purpose the improvement of the relationship between man and machine, and this occurs both by overcoming the operational barriers - such as the alphanumeric keyboard or other peripheral devices - and through the development of machine behavioural models which adapt themselves to its user.
These guidelines have wide applications in music and the research is based both on the ergonomics and the kinds of interfaces, and on the software environments development which integrate the sound fruition with the visual and tactile ones .

The term “Interactivity” is referred to the relationship between man and work, in particular those features which allow the data entry by the user. We can define interactivity as the characteristic of a system whose behaviour is not fixed, but varies according to user action. When a user conveys an information to the artwork, he "interacts" with it and, as a result of this interaction, the artwork can change its predetermined behaviour to adapt to the new requests.
The term "interactive" is normally used to identify those systems which respond to the user action in a deterministic way. The most typical example of an interactive system is the computer: the programmes working in it allow a user to perform actions and receive predictable answers.
In the interactive work, the user is facing a predefined simple or complex organism. The answers he may receive or the processes he may activate are a consequence of the actions he performs. The user has the freedom to choose the sequence of actions to be performed, he can follow his own logical and intuitive path which led him to creatively work within a vast but finite set of possibilities.

The term “Adaptive” identifies a system which "self- adjusts" according to the user action and the conditions of the surrounding environment. An adaptive work receives and/or perceives the outside stimuli and changes its status, its answers in an unpredictable or partially predictable way. The user will receive responses which consider not only his current action, but also the sequence of the previous actions and the whole environmental context. The work is to some extent able to "learn" and "adapt" to the needs or the conditions around it. Typically, in these works, the user has the freedom to choose the sequence of actions to be carried out but the results are irreversible, that is that to a stimulus, carried out at different times, an equal effect will no longer correspond.
This is the case of works such as Volumi adattivi, Trio plastico and In coro where the music is self-organized according to the combination and speed of the actions carried out by the public, to the proximity of objects or bodies, to the position and pressure of the mobile sculptured parts (sensitive plates).

The term “Evolutive” identifies a system able to self-adjust, to create and/or modify its calculation processes, to store and process the previous conditions and to change its own behaviour according to the user input and to those which derive from the environment and the flow of time.
This type of work can be compared to a simple and primitive living organism, destined to - like all living beings - a limited temporal cycle, if that has been decided by its authors.
It is an approach of remarkable artistic and scientific design complexity since a work which presents such an high “openness” characteristics is more exposed to the loss of identity, style which refers to its author, as well as to the self-analysis processes deviation [5].
Today, at the CRM, software control algorithms for interactivity and adaptivity of musical-sculpture works of art have been implemented. The evolution system of this works is matter for study and a significant application has been realized with OASI.

The musical thinking and the expressive innovation

The sound
The sound can bring the material vibration means to our knowledge (ie, a string, a plate, a membrane, a smooth or gear wheel, a door), makes the shape, the elasticity, mode-exciting of a vibrating object easy to guess, without necessarily seeing it or touching it.
The sound provides us general spatial information about position, distance, movement of a sound source (ie a voice that goes away).
The mixture and the variation over time of the perceivable components of sound (tones, timbres, intensity, durations) allow us to recognize its causal or accidental origin (ie the thunder or the interference noises of the radio), of even to go back to the state or intention of those who produce it, whether its source is human or animal (ie, the laugh, a cry or a yelp, a growl).

The music
The information conveyed by the sound is based on memory, on the sensory and cognitive experience recall, but the sound is also able to stimulate imagination with totally new, abstract and changing information. Its evocative quality can be conveyed by musician to arouse emotion and its organization over time, along with other sounds, can become a vehicle for an intuitive knowledge and for logical relationships.
The sounds, ex novo created by the computer or usual as the musical instruments ones, when they are composed, organized in space and time, become diachronically and synchronically clear for our attention and considered as music.
We typically ascribe to the music the quality to touch us, to stimulate the mental and physical system, to fulfil a complex set of feelings and cognitive links and personal perceptive connections.
But the music also conveys a shared sense of cultural references, of collective, ethnic, social identity, of religious and ethical values; in other words it is an expression of the civilization which has created it, like all arts do, but with a crucial difference: it is immaterial, or intangible, invisible, abstract.
This quality makes the music able to immediately touch the emotional sphere, to support and stimulate the imagination in order to set free the creativity and the ancestral impulses, to stimulate the representative activity of the thought with abstract metaphors related to the lived experience.
Music can transform the perception of space and time, can build a places and forms memory.
These aspects are fundamental for the musical works concept which have active forms of fruition, which provide for the interaction with the listener or a path, a change in sound features according to the environment or to an arbitrary choice of position and listening conditions.

To hear is an involuntary act for man. Hearing constantly monitors the world around us, is oriented in any directions, and indiscriminately perceives every kind of surrounding acoustic stimulus. This shows how listening, instead, is a voluntary act, which manifests itself as an addressed attention over the time; this last makes the listening act partially selective, directed toward the sound sources involved and, above all, predictive. Listening means, for the music, engaging, in a conscious way, the perceptive organ (sense of hearing) and the cognitive one (mind); to this awareness, related intellectual and psychological attitudes are added, qualities able to arouse emotions and to activate those intuitive and deductive faculties which identify the origin and the distinction between the sounds, their spatial-temporal distribution and the expressive characteristics.
As for the traditional musical works, so listening in a consciously and active way means to follow the logical and consistent flow of relationships between sounds, but in the case of adaptive works, the sensory stimulation extends, as it functionally combines the sound to the tactile and visual experience; in general the work is perceived as a dynamic, emotional and learning process where participation is intentional and where we are partially responsible for.
Considerations expressed so far are clear for those who turn their attention to the listening or the musical creation: they represent the common conceptual basis which allows the appreciation and enjoyment of the music. If this conceptual basis, however, is extended, or if the sound, the music and the listening make interdependent their functions, in other words if the sounds, the music and the fruition mutually become one the cause of the other, in a dialectic relationship which generates an interactive work with the listener - adaptive with the surrounding environment, and evolutive over time – so we can cautiously enter into the ideational scenario which originates the musical-sculpture adaptive works.

State of art

Material and vibration
The knowledge and resources heritage available to the musician in the last forty years has originated some changes in sounds, musical form, and ways of listening; transformations, with different meanings, are evident in all kinds of music up to define a style according to the type of sound, a way of listening according to the type of music. Always considering the reasoning about the re-establishment of the composition procedural patterns made by the computers, we can say that a decisive stimulus, for the knowledge and the creative application on the sound, has been given by the vibrational study of the material carried out by the physics. Geometry, dimensions and material of a vibrating object are responsible for the timbre, the pitch and the temporal evolution of a sound. These information result into musical works that integrate music with the physical characteristics of the materials and their forms. This is the case of the works based on Planofoni ®, vibrating planar devices made of different material (ie metal, harmonic wood, paper, plastic, glass etc.), designed at CRM - Centro Ricerche Musicali in Rome, which realized a total interdependence between the plastic and musical elements, giving thus a unifying principle of aesthetic nature to the listener, as well as functional, that is able to diffuse the sound replacing the traditional loud speakers.
The Planofoni® (Lupone, Musica Scienza 1998), are not loud speakers, they diffuse the sound with results which depend on the material structure, the design geometry, the positioning and curvatures of the surfaces and on the plastic volumes occupied. The Planofoni allow the sound to have the timbrical characteristics of the material used and allow, through a punctual irradiation on the whole surface, to draw the acoustic space in relation to the architectural one. Designed as an "art installations", and derived from the studies on the vibrational qualities of materials, conducted by the CRF - Centro Ricerche Fiat - in collaboration with the CRM (1993-96), the Planofoni® are designed to integrate the emerging aspects of the visual and sound perception (shape, material, sound, language and expression) in order to give life to a new way of creation, and fruition the work of art and music.

The relationship with the nature
The computer use in music has meant conceiving, without interruption, sounds and musical forms which include them. It is to say that the process that synthesizes sounds can advance up to determine the complex relationships between them, leading to the musical work structure and form. It is a deep coherence that inextricably links the micro and the macro structure of a work, able to give unheard expressive and sound solutions to the listener.
In the same way we can also conceive the transformation and evolution of sounds taken from the natural world. The real sound, exposed to virtual transfiguration processes and evolutions, different from those identified as own and unavoidable, may assume extended evocative values and ambiguous semantic references as in the case of the synthesized sound. If its evolution over the time is consistent and while listening is manifested as an implied need, as a logical consequence of the relationships between the parameters which comprise it, so the sound may become a "sound-form", may be perceived as a completed sound with a peculiar destiny, a significant and directed structure, a self and emotionally meaningful development not necessarily related to what temporally precedes or follows it.
The elaboration process in this case deeply affects the physical characteristics of natural sounds, analyses the significant features to change, as a consequence, the proportional weight of the sound parameters and their evolutions over the time. This is the case where mutations respond to laws and procedures consistent with the sound material, derived from observation and experimentation of the composer who directs the expressive results.
The music, conceived by transforming the sounds of a given natural environment, if properly diffused in the same environment, can be integrated to the sounds context which originated it, multiplying references and links within the musical texture, expanding the perception of the acoustic space where the listener is placed. If the stimuli offered for the fruition reach the sensory complex in a consistent way, that is, if the relationship between the music and the environment fulfil organization criteria of concordance, relevance, correspondence or logical contrast, a synesthesia which correlates listening to the sight, smell and touch senses will be more easily to achieve.
Some of the above mentioned observations represent the basic idea of permanent musical-sculpture works designed to natural and urban environments.

Urban environment
Conceiving an adaptive music, able to change sounds and shapes according to the acoustic, luminous, atmospheric context and the time flow, means giving to the listener a constantly renewed and vital experience of fruition. When this music is integrated with architecture and urban environment, with sculptural and plastic elements able to produce and convey the music in an articulated way into the surrounding space, the perception of the place becomes dynamic and the fruition is stimulated to comparison, to memory and to prediction.
Public art in a public space is a concept, but it is also a high purpose which turns its attention first of all to the life quality; in this inquiring and creative context that concerns artists, architects, scientists, we feel the need of renewing the emblematic urban sites, of welcoming, accompanying, gratifying the existence of the man with high and civil expression.
The music, intangible and changeable, can satisfy these needs as happened for the pilot project in Belgrade. The musical artwork was conceived with the intention to become a continuous interpreter of the present. It shall not immobilize its own expressive status, not efface but preserve and revise the shapes and sounds heritage to which it gave life, contributing thus to subvert the perception of a frozen time - typical of the monumental and representative works -, in order to establish an immanent relationship with the listener, to actualize the sharing of the meaning and the stimulus to the imagination.
The musical concept described above requires a profound reflection which affects as the form as the sound nature. The adaptive music identifies a music which self-adjusts according to the surrounding environment and the previous conditions, able to perform a kind of "learning" that enables it to choose, to combine, to irreversibly but coherently transform the sounds which make it up.
According to these criteria the work Muzika i Forma for the Slavija Square in Belgrade (Lupone, Galizia, Djukanovic, Terzi, 2008).

Interactivity and evolution
An interactive music which could evolve as a mere organism requires an open formal conception, inclined to the dialogue with the user, but also strong self-analysis processes, selective and distinctive abilities compared to useless or damaging input. The design approach is complex and not just musical: it requires a patient experimentation and cataloguing of the logical connections which link the work response to the human gesture which provokes it, requires a relevant and related data sensor processing which influence the interactive behaviour.
Obviously defining all the properties that can rule this kind of work is not the prevailing purpose. What matters in this case is the stylistic maintenance of the musical style, the preservation of the work identity, compared to a broad acceptance, a simple, predictable operative mode by the user, and the widest range of useful responses (perceptible changes).
The evolutionary aspect encloses some of the most interesting creative aspects from the musical point of view: the ways in which the work evolves are marked in a series of low-level rules of composition, a kind of generative grammar that informs and constitutes the musical texture.
Using this approach the musical and sculptural work Blu Armonico (Lupone, Galizia, 2008) has been conceived for the city of L'Aquila.


[1] L. Bianchini, Designing a virtual theatrical listening space, ICMC 2000, proceedings, Berlin
[2] M. Lupone, Musica e Mutazione, in HiArt, vol. 1, 2008, Gangemi Publisher, Roma
[3] J. Paradiso, Electronic Music Interfaces, 1998, MIT press, Boston
[4] Y. Nagashima, Sensors for Interactive Music Performance, ICMC 2000 proceedings, Berlin
[5] P. Inverardi, P. Pelliccione, M. Lupone, A. Gabriele, Ad-Opera: Music-Inspired Self-Adaptive Systems, in Computation for Humanity: Information Technology to Advance Society, 2013, CRC Press