Interface - By Paul Doornbusch

A controller is that part of an instrument, acoustic or electronic, left if we remove the production of sound. It is the part of the instrument the performer “plays”. The controller or interface is an extension of the performer’s body. While this is called an “interface” we should remember that musicians have very intimate relationships with their instruments – they exert significant energy with it, they share their saliva and sweat with their instruments – and the instrument should be capable of capturing every nuance of their control gesture and translating that into an expressive sound. Instrumental performance gestures are extensions of physical and vocal gestures.
Making a computer based musical instrument that matches a mechano-acoustic instrument in these regards is not an easy task because when designing, working with, or listening to computer based musical instruments we are directly confronted with the abstractness of the computer, which seems at odds with physical and gestural intimacy.
That this is the way music is heading is undeniable, which is why this is such an important field of musical research.

At the outset of designing an electronic instrument controller there are a myriad of choices available; knobs or rotary and linear controllers can be used, proximity detectors (for large and small distances), pressure sensors, video cameras, joysticks, turntables, accelerometers and so are also available. It is important to design the instrument to fit the gestural behaviour and the musical intentions. This will narrow the range of sensible options for the controller and a final design will only be possible with a degree of experimentation and analysis. Controllers need to be selected that make maximum use of the physical gestures, while not minimising them or making them meaningless or trivial.

The interface or controller can be in the form of a traditional instrument, where sensors are used to detect the gestures of the performer. An example of this would be a wind instrument where the closure of holes or keys and breath are detected via sensors and the information used to control a synthesis engine. Another traditional instrument, which can be used as a controller, is a keyboard and commercial manufacturers make many of these. Traditional instruments may also be modified to add new controllers, such as a joystick or light sensor added to a guitar (as practiced by Tom Fryer) or an accelerometer on a percussionist’s sticks. Other controllers may take completely new forms such as Michele Waiswisz’s and Laetitia Sonami’s hand controllers and the instruments of the Sensorband. Some tools, such as fader boxes, game controllers and control surfaces, may also find use as gestural interfaces for computer musical instruments. Some of the most interesting current research is in using force-feedback mechanisms (from game controllers) to provide physical feedback for the performer. This opens completely new territory in the field of expressive control interfaces for musical performance.

There is no “free lunch” with computer instrument controllers (or computer music for that matter) – it is at least as difficult to build and play a worthwhile and non-trivial digital computer instrument as it is an acoustic instrument.