Feedbacz (2006) is a structured improvisation for saxophone and computer inspired by Steve Baczkowski. It can be performed with a 4-channel or 8-channel playback system. A number of spectral processing techniques are employed to alter the sound of the sax in real-time. One of the techniques involves what I call a spectral freezer. As the performer is playing the audio is transformed into the frequency domain and snapshots of overtone information is recorded into a series of different buffers. The information stored in the buffers is then fed through a feedback loop before being transformed back into the time domain. The results of this process produce resonating (i.e. frozen) overtones. The fundamental pitch and amplitude of the instrument are also tracked by the computer. This information is used to feed the XY coordinates of a multi-channel spatializer in order to move the sound of the saxophone around the space. Other aspects of the piece involve more traditional processing tools such as cross-synthesis and ring modulation.
This recording is from a performance by Masahito Sugihara in Lutkin Hall at Northwestern University on November 5, 2006.