The design of traditional acoustic musical instruments is in many ways dictated by the physics of the method of sound production used in the instrument. That is, certain constraints are placed on the designer of the instrument which influence the physical form of the instrument. For example, to produce a certain frequency range with a vibrating string, we must use a string of specific length, held at a specific tension. This requirement limits the design possiblities of the instrument.

For digital musical instruments (DMIs), on the other hand, such limitations do not exist. The sound production is performed by a computer-based sound synthesis system, which can be used to produce any sound. The parameters of this sound (for example the frequency, amplitude or spectral content of the sound) are available as controls which can be mapped to any input the designer might wish. In a software-based instrument these parameters might be controlled with the keyboard and mouse, through on-screen sliders and knobs, or with a generic controller such as a graphics tablet or joystick. For a DMI, these parameters can be controlled using a sensor (or a combination of sensors) which form part of the physical interface of the instrument.

A DMI may be seen as consisting of 3 main components:

• The physical interface containing the sensors, actuators and physical body of the instrument.
• The software synthesis system which creates both the sonic output of the instrument and any visual, haptic and/or vibrotactile feedback.
• The mapping system in which connections are made between parameters of the physical interface and those of the synthesis system.

The focus of this research project is on design of the physical interface component of a DMI and in particular on improving the performer-instrument interaction through careful design and evaluation of the physical interface. As such, it involves two sub-areas of research, these being:

• An examination of the suitability_of_sensors for specific tasks in digital musical instruments, with the goal of developing guidelines on the optimal use of sensors in the physical interface of a DMI.

• An investigation of vibrotactile_feedback in digital musical instruments, concentrating on the choice and use of vibration actuators to transmit vibrotactile feedback to the performer.