We describe three new music controllers, each designed to be played by two players. As the intimacy between two people increases so does their ability to anticipate and predict the other's actions. We hypothesize that this intimacy between two people can be used as a basis for new controllers for musical expression. Looking at ways people communicate non-verbally, we are developing three new instruments based on different communication channels. The Tooka is a hollow tube with a pressure sensor and buttons for each player. Players place opposite ends in their mouths and modulate the pressure in the tube with their tongues and lungs, controlling sound. Coordinated button presses control the music as well. The Pushka , yet to be built, is a semi-rigid rod with strain gauges and position sensors to track the rod's position. Each player holds opposite ends of the rod and manipulates it together. Bend, end point position, velocity and acceleration and torque are mapped to musical parameters. The Pullka, yet to be built, is simply a string attached at both ends with two bridges. Tension is measured with strain gauges. Players manipulate the string tension at each end together to modulate sound. We are looking at different musical mappings appropriate for two players.

This project is open for 496 projects to continue to improve Tooka and/or make Pushka and Pullka. Musical knowledge is an asset.

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Tooka

The current version of the Tooka uses two identical sections of hollow flexible tube connected together with a plastic connector to form one continuous tube. At each end is a mouth-piece made from a connector, four buttons and a pressure sensor. The tube's outside and inside diameters are 1.25" and 1", respectively, providing a fairly high compliance. When assembled, the Tooka measures 86cm long. Attached to one side is a bend sensor, which responds to flexing of the tube. An air pressure sensor in the center measures the air pressure inside the tube. Blue velvet coverings and black tape on all the wires were added by one of the musicians to improve the visual and tactile aesthetics for the performers. The instrument is shown in Figure 1. Two people demonstrating how to play the Tooka are shown at the top of the page.

To play the Tooka, each player puts their mouth over opposite ends forming a sealed tube. The players collectively modulate the tube pressure to control sound. Each player has four buttons: two black buttons are for notes. The white button is for octaves. Collaboratively players can play more than four octaves. The red button is for capturing/sustaining the sound. Using red button, players capture/sustain the current sound (note + modulation). Collaboratively, players can create layer of sounds as a drone. Each player has a thumb pressure sensor for vibrato. Bending the tube bend the pitch through bend sensor attached on the tube. Players can modulate the pressure in the tube using either their tongue, cheeks, velum, or diaphragm.

The Tooka's air pressure sensor is a NovaSensor 410-015G3L that detects medium range pressures. The air pressure sensor is connected to an instrumentation amplifier and the signal is passed to an I-Cube from Infusion Systems. Both hardware and software calibration are used for this sensor. The buttons are also connected to the analog inputs of the I-Cube but they are thresholded to behave as digital inputs. The bend sensor and two thumb-pressure sensors feed into the analog inputs of the I-Cube. The I-Cube feeds data from the sensors into a Pd patch. All the music code for mapping sensor data to MIDI control codes is performed within Pd. The Yamaha sound generator receives the MIDI commands and plays the sounds according to how it is programmed. Figure 2 shows a block diagram of how the system works.

The first version of the Tooka appeared at NIME02 as an experiment in two-person musical instruments (see download section). Through collaboration with musicians and engineers, we evolved the design to meet the needs of the musicians as they practiced. The current version incorporates all the changes requested at this point. The musicians are now able to be expressive with the instrument and have performed with an ensemble of traditional instruments as well as on their own.

Here are some images of the Tooka system.

Figure 1: The Tooka.

Figure 2: Block diagram of the Tooka system.

Pushka

We are currently investigating a second two-person instrument to see the effect of different feedback and form has on expression and experience. The current version of the Pushka envisioned is a semi-rigid rod held by each player. Strain gauges are placed on the rod to measure the flex in the rod as well as the torque on the rod. As well, the ends of the rod are tracked using a magnetic tracker. These sensors provide position, velocity and acceleration of the rod's ends. A diagram of the instrument is in figure 4. To play the Pushka, each player holds the ends of the rod in their hands. The semi-rigid rod connects the two players directly. Collectively, they pull, push, move and twist the rod to control music. By coordinating their movements in opposing direction they can provide effectively an isometric force controller. By coordinating in the same direction they have an isotonic controller allowing position, velocity and acceleration to control the music. The coordinated interplay between the players provides a large degree of control over the musical spaces. The instrument has many desirable features:

• it affords a large musical mapping space;
• it provides force feedback to each player through the rod
itself;
• control of the instrument is easily visible for each player as well as the audience.

Figure 4: Conceptualization of the Pushka.

Pullka

While the Pushka allows push and pull forces to be exchanged between players, we envision a third type of two-person instrument that uses only pull forces called the Pullka. The current vision of the Pullka is a single string (or more) held under tension with a bridge about 1/5 of the way from each end of the string. A picture of the instrument is in Figure 5. A strain gauge measures the tension in the string. To play the Pullka, each player pushes on the string behind the bridge at each end. The string connects the two players directly through the tension on the string. The string we are currently using is not meant to be plucked or strummed; however, this is a simple variation which we intend to explore. Collectively, players push on the string to control music. The coordinated interplay between the players provides a large degree of control over the musical spaces. This instrument highly constrains the control space. We do this to explore a reduced control space to see how much expression is possible with only a single parameter. The string does provide direct feedback between players suggesting the possibility for an expressive controller.

Figure 5: Conceptualization of the Pullka.

For 496 Project students: Skills Useful

• Instrumentation
• jMax
• Music theory
• Audio synthesis

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