The Brainstem Cello is an interactive instrument that explores the relationship between musician and sound object. The cello monitors a performer’s actions and responds in various ways to influence the performer, and to create and modify sounds.
The original idea for the Brainstem arose from thinking about combining two musical relationships: the communication that occurs between improvising musicians, and the connection between a performer and her instrument. The cello aims to create a situation in which a musician is reacting to changes in her instrument as she might react to another performer in an improvised situation.
In addition to this interactive environment, the instrument has a number of other exciting applications. Though always intended to involve a live performer, the Brainstem has sound-producing elements that allow it to function as a solo robotic performer, or as an installation. The cello can also create a duet, with a performer and manipulator interacting through the instrument. In this situation, the two musicians are influenced by each other, but the focus is on the way that each person’s actions on the instrument affect the combined sounds. Lastly, the instrument has exciting potential for compositions, with the mechanical acoustic effects of the instrument replacing (or combining with) real-time audio processing.
The Brainstem has three types of sensors to monitor a performer’s actions. The finger board has potentiometers that track finger positions on each string. There are two infrared proximity sensors to monitor bow movements. The bridge has piezo microphones to determine which strings are producing sound, and what types of sounds are being produced.
The instrument has many active mechanisms to create sounds on the instrument. DC motors rotate to make coarse bowing-like sounds. Solenoids strike the strings, creating pizzicato-like sounds. Both of these effects can also be used to modify the sounds that a performer is creating. Additionally, there are various activators mounted on the body of the instrument to make a variety of mechanical sounds.
The instrument also has components specifically intended to affect the sounds created by a performer. There are bow-interrupters that prevent the bow from touching the strings. These can be used in short bursts to add rhythm or tremolo to a slowly bowed note, or can be engaged for longer times to silence the instrument. Two servo motors control a mute for the strings. When lightly engaged, this adds a buzz to the sound, and when fully engaged the sound is significantly dampened. Lastly, there is a mechanism that allows the instrument to re-tune itself mid-performance. Four stepper motors adjust the tensions on the strings to change the tuning, beyond the control of the performer.