Spinning Magnetic Polyphonic String Resonator

Made to resonate steel stringed instruments through the process of magnetic strumming. Ferrous’ spinning disc contains six strong earth magnets. Adjusting the rotational speed of the disc will change which strings are most affected and their harmonic content. If the disc is spinning slowly lower strings resonate; if the disc is spinning quickly higher strings will resonate louder. The results can sound like an unknown instrument in a reverberated physical space, floating sine wave tones, or feedback. Fluctuation of rotation speed by using the thumbwheel, rev button, touch-plate or control voltage input can create a soft strumming effect across multiple strings or shifts in harmonic content. New harmonics and overtones can emerge from both lower and higher strings as the disc spins faster.

The distance at which Ferrous is held from strings affects how strongly they will resonate and their harmonics. If Ferrous is placed near guitar pickups you will hear the heavy sounds of spinning magnets and the motor with the resulting pitch based upon the disc’s RPM.

What It Can Do

• Sine wave-like string resonance + harmonic overtones
• Pitch modulation / pitch bending behavior
• Pseudo feedback tonalities
• Polyphonic “magnetic strumming” of strings can be achieved by starting the disc at a lower RPM and pulsing the motor faster, either with the “Rev Button,” the “Thumbwheel,” the “Touch Plate,” or the “Control Voltage Input”. Magnetic Strumming not only affects the fundamental pitch of a string but can be heard affecting and accentuating various harmonic overtones.
• ”Pitch blending” interactions between dominant resonant string(s) pitch and brushless motor speed. As the motor/magnet RPM speed comes into “alignment” with the resonance of surrounding strings, you will sometimes hear two pitches beating against one another before sliding/bending into place, resulting finally in a swell in volume and greater string vibration. This can be happening to multiple strings simultaneously.
• Multiple strings can be affected while the RPM is steady. For example, you may hear the fundamental pitch of multiple strings resonating while higher harmonics are activated on others. Different RPMs can provide different additive harmonic combinations between the same strings (or chord) being held.
• There are three small magnets and three larger magnets aligned in overlapping triangular patterns on the disc. The smaller magnets help provide higher-order harmonics and the larger magnets help create greater string movement and lower-order harmonics.
• Higher RPMs often lead to higher strings resonating and higher harmonic overtones. Lower RPMs often lead to lower strings resonating and less harmonic overtones.
• When using Ferrous with an electric guitar (or other instrument with pickups) the preferred placement is above the fretboard. Keeping the rotating disc at least 5” away from magnetic pickups ensures less of the motor sound mixing with the resonating string sound (unless this is a desired effect).
• When using an electric guitar, placement lower on the neck can create interactions between magnetic disc and pickups with overtones of resonating strings. When placed directly over magnetic pickups, pitch is derived from the rotation of the magnets, and the volume is derived from the distance between Ferrous and the pickups. **Never place the magnetic disc directly onto pickups because this can damage them.

Specifications:

• Size: 5.25” x 2.5” x 1” / 13.33cm x 6.35cm x 2.54cm
• Weight: 0.4 lbs / 0.15 kg
• Materials: Birch plywood encloser + PCB/Fiberglass interface and disc + neodymium magnets + repurposed hard drive motor + negative space cutouts for exposed battery access.
• Controls: Thumbwheel for speed adjustment (+ on/off). Pushbutton for momentary full speed RPM or pulse. Touch-plate for pressure sensitive speed control. Control Voltage input for external speed control.
• Visual: Downward facing yellow LED for string illumination
• Assist 1: A provided threaded standoff with rubber tip can be added near the LED as a fretboard rest between strings. This stops the disc from touching guitar strings and provides a more controlled experience.
• Assist 2: Four small rubber feet which can be added to the four screws using a phillips head screw driver. These can be useful for instruments with many strings like Pianos and Zithers. The feet can rest on surrounding strings as the disc resonates strings below.
• Power: **9v Battery

**Ferrous ships with a rechargeable 9v battery. As a bonus the (mini)USB charging port is left exposed so you don’t have to remove the battery during charging. Be wary of some 9v Rechargeable batteries (and particularly those that are less than 1300mAh) as some may not be able to provide enough power to properly power the brushless motor. ***Also note that 9v Carbon Zinc batteries do not supply enough power!