use qualities relative to the participant's interactive
experience ; transparency, social-action space, user
control/ autonomy, pliability, playability and seductivity
. Interaction should be designed to enhance a
participant's control and, thereby facilitating interest
and motivation. Action cycles inherent in the interaction
create a process of enticement by attracting the
participant's attention, ability to make progress and
experiencing fulfilment by ending the experience in a
positive way. Thus, the person is seduced by the
system's playability offering surprise and prompting
emotional responses through interactional beauty  of
3. MUSICAL TOPOLOGY OF THE
Realisation of therapeutic benefits outlined above
requires innovative installations with potential for
meaningful music making within constraints imposed by
the music maker's disabilities. Critical issues are
respectively discussed in this and section 4, i.e., the
design of the 'keyboard' of an 'instrument' and the
means of 'playing' it. Here we discuss the concept
musical topology, as has emerged through the work of
Rolf Gehlhaar on his SOUND=SPACE installation .
A musical topology results from analysis and
processing of information gathered from movement of
bodies in a space equipped with sensors. The
information is fed as control variables to compositional
algorithms, and via synthesis routines, produces sounds.
Thus, the audience becomes the performers.
These topologies are passive, active, or hybrid. An
example passive topography is simple triggering of a
sound(s) with specified duration(s) by a person stepping
into the area to which the sound(s) is assigned; like
walking on imaginary keyboards that span the space.
The 'instrument' is deterministic, playing only when
someone triggers it, sounds 'mapped' onto the space by
the program. Each 'keyboard' can be structured
independently or assigned to a group of keyboards in a
specific region, each with different pitches, durations
and sounds assigned to the 'keys'.
An active topology comprises an algorithmic realtime composition by the computer, influenced by
presence and movement of persons in the space.
Movements are converted into control parameters of the
composing algorithm. The effect is like conducting an
ensemble of musicians: usually, greater activity results
in more animated and complex music. The algorithm
employs interlinked chains of probability matrices,
which can be programmed to produce generic musical
The hybrid topology combines both of the above into
a space that reacts not only to movement but also to
position. The effect can be like controlling tempo or
direction of a musical flow by moving about the space
and, at the same time, triggering specific events by
stepping into specific places.
SOUND=SPACE implements the above topologies
as a musical 'instrument' 'played', usually by several
persons in an empty space surveyed by an ultrasonic
echolocation system that detects positions and
movement of people. These measurements are sent to a
computer that converts them into sounds. Normally, the
space is square (up to 10m x 10m) sufficient for 8-15
people. Sensors on two contiguous sides look inwards
across the space, creating a 'grid'. Thus,
SOUND=SPACE is a complex, sophisticated multifunctional, multi-user system; but its environment is
uncomplicated, friendly and non-intimidating. When
invaded, it responds immediately with sound. No
expertise is required to create generally exciting,
engaging and pleasant sounds and musical sequences.
Since moving in space is key to playing this musical
instrument, users improve their perception of space, and,
consequently their capabilities of movement. Accuracy
only becomes a requirement when an intentional
(musical) gesture is desired. Thus, SOUND=SPACE
allows musical expression with no special skills while
promoting development and improvement of new skills.
Potential for benefiting people with disabilities
emerged during an installation at the Gulbenkian
Foundation, Lisbon in 1986. A visit by disabled children
from special schools was such a success that it catalysed
Gehlhaar's intensive involvement with
SOUND=SPACE in the world of disability. He came to
understand that technology no longer allows us simply
to make art for a public; it demands that we create
opportunities for the public to make art. It is about
creating situations that encourage active, creative
response common to all humans, able or disabled.
Accordingly, he redesigned SOUND-SPACE to tailor
the interactive aspects more towards the highly varied
skill sets of disabled users.
A further dimension emerged during recent
SOUND=SPACE workshops run by Luis Miguel Girao
in Oporto, Portugal, as part of "Ao Alcance de Todos".
The system was set-up for participants suffering from
brain paralysis, educators and music students, in a
public space that also allowed interaction with passersby. This highlighted SOUND=SPACE as a social
environment also including, perhaps more importantly,
interaction between person and person (disabled or nondisabled) while 'playing' in the environment. Thus, it
was evident that non-disabled people had much to learn
from disabled people about awareness and sensitivity to
the musical environment.
Finally, we note that environments, such as
SOUND=SPACE, have an educational role. Techniques
of progressive exploration of the instrument reveal basic
principles of playing music, such as: sound/silence,
musical phrase and musical dialog. A deeper approach
brings up the learning of harmony and rhythm.
Gehlhaar has developed different versions of the
topographies, each with its own characteristic mood and
nature - calming, exciting, sustained, rhythmical,
percussive, and so forth. It is possible, within a
workshop, to move rapidly from one mood to another,
with few words spoken, to encourage participation, to
support the mood and activity of the moment, to focus
attention or to shift the concentration of the participants,
to calm them down when they get too excited.