The original turntable acquired for this project
Home | Concept | Body & instrument | Optical tonearm | Turntable platter | PIC code | Review
All of the above sensors and controls are monitored and automated by the USB-attached computer, using the CREATE USB Interface, and control software written in Max/MSP. Further digital processing and analysis of the audio can therefore be integrated into the system.
The stringed instrument can be played with fretless slide and using the high-register fixed tuning strings. The audio collected from the stylus and the contact mic is routed to software in Max/MSP. The patch currently used for processing the sound performs pitch estimation and resynthesis (one octave lower) using filtered saw-waves, with delay and reverberation.
The turntable can act as a 'scratching' interface for controlled pitch-shifting, and as a pre-recorded pattern controller. By changing the platter speed and distance of the optical tone-arm from the platter center over time, many circular tracks of data may be mixed to create non-repeating structures. The data from the optical tone arm is being written into a video matrix in Jitter, and is used to modulate the phase vocoder playback parameter in Max/MSP.
Originally the project had been conceived to also incorporate magnetic tape heads to explore the possibilities of malleable physical recording, using opened 7.5" floppy disks mounted on the platter as the medium. We built the necessary bias signal (80-150kHz sine ideally) for the erase and record heads, using a digital timer and filter circuit. After spending two weeks attempting to reconstruct tape recording using the floppy disk, it became clear that the fidelity was so poor that it was not a viable technology to incorporate into the project.
Static noisemaker: In the process of building audio amplifier circuits based around National Semiconductor LM1877N amplifier chips, it became clear that the noise floor of the circuits was unacceptably high (not to mention unpredictable). Acknowledging the importance of noise, error and glitch in the history of audio technology, we considered incorporating this circuit as a further audio source into the turntable interface, using human conductivity capacitance as the sensor medium.
Further extensions to the project not yet investigated:
The original turntable acquired for this project
Work in progress...
Inside view of completed project