The Radio Drum
Progress Report 1
Progress Report 2
Analog signals from the Radio Drum are band-limited to 700 Hz. Since a human is not capable of drumming faster than once every 40 msec, the gesture signal should not be faster than 250 Hz. These characteristics are taken into consideration in the filter design and implementation. These filters are created in a program called MAX/MSP located on the host computer.
MAX/MSP is a combined MIDI/Digital Audio programming environment. This application allows manipulation of real-time audio and also acts as a MIDI development environment. MAX is an object-oriented programming environment for manipulating MIDI data. MAX allows the user to create "patches" by placing functional objects on the screen and connecting them in different ways. MSP is a set of extensions to MAX, which allow the user to manipulate digital audio in the same ways that MIDI data is manipulated.
Filters would enable mapping of a MIDI-controlled musical component to a certain gesture, for instance a strike in the z direction. The strike could be associated to a change in pitch, timbre, tone or it could trigger a sound or series of sounds. The filter will allow the instrument to function in a more sensitive manner so that all the expressions in the performer’s gestures are captured.
An algorithm could be used to generate a trigger pulse when a strike occurs. There would be two stages to the algorithm: the matched filter, followed by a peak detector which finds the points where dz/dt = 0 and d2z/dt2 < 0. The matched filter matches the pulse shape using a FIR filter with guassian impulse response. The guassian form is a rational approximation of the pulse shape of a drum roll.