Sitar

Electric Guitar

Acoustic Guitar

Electric Bass

Acoustic Bass

Piano

Veena

Urhu

Mandolin

Violin

Cello

Banjo

Auto-harp

Double Bass

Harp

Pedal Steel

Kalimba

Psaltery

Zither

Baglama

Swarmandal

Resonant Steel/Iron everyday objects

Resonant non-steel objects (when used with earth magnets attached to or sandwiching said objects)

+ other instruments with steel strings not yet tested

*All listed above must be of the steel string variety

-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.

-It can take some time to get used to placement, distance, holding methods and how your instrument and chord changes interact with the RPM/Speed of the spinning disc. After you familiarize yourself with this interplay the results will be much more rewarding and responsive. The disc is designed to hover very close above the strings without touching them.

1. Charge the included 9v rechargeable battery for 1 hour prior to use (the LED on the battery should turn green or blue).

2. Inserting the battery: Turn Ferrous so the wheel faces the floor now insert the battery and push it until it clicks into the terminal. *Removing the battery: Using the tip of a pen or a small screw driver, locate the small divot between the +/- symbols. Now gently pry the battery outwards using the divot to pry against. You can use your thumbs to slide it the rest of the way out.

3. Hold it in your hand and turn the black thumbwheel (*click) and the Yellow LED on the Ferrous should turn on and the magnet disc should begin turning. Sometimes holding the blue Pulse button during startup can provide a smoother start. **If your Ferrous disc doesn’t want to spin or has trouble starting up it could be a weak or damaged battery. (see “Specifications” tab below for details).

4. Feel how the thumbwheel control changes the speed of the disc and how the blue Pulse button “pulses” the RPM faster, try shorter and longer button taps for different string interactions.

5. While using the thumbwheel to “search” for new harmonic interactions you’ll notice how sensitive the relational interplay can be between the disc and strings/notes. A lot of interesting interactions at times can be found by very small speed adjustments with the thumbwheel.

6. A very important thing to note is that every time you change the RPM on Ferrous or a note/chord on an instrument the interaction between them has shifted. The results between instrument to instrument will also be different based on specifics like string thickness, string iron content (more is better! some Cello and Violin strings have low Iron content we've found so less movement).

IMPORTANT: Be careful never to touch the magnetic disc directly to electric guitar pickups. You could potentially de-magnetize them!

6. Hold Ferrous about 1/2” (1.3cm) from the steel strings while the disc is rotating. Move closer or further away to adjust volume/resonant strength. When placed close to the strings the result can be strong string vibrations resulting in the strings colliding with the fret board or the rotating disc.

7. When Ferrous is held close to the strings of an instrument you will feel the strong magnetic pull. For guitar, one stabilization method is to use the thumb and pointer finger by resting them on the outside edges of the fretboard. This acts as a way to ensure proper distance between the strings and rotating disc.

8. Pulse speed from low to high to 'magnetically strum” multiple strings.

9. Use the threaded standoff (with rubber tip) as a rest between strings on a guitar fretboard for more relaxed and controlled playback.

10. By holding Ferrous 90° to the neck of a guitar, one can use their ring finger and pinky to modulate speed with the touch-plate below. To do this you should set the RPM slow.

11. Hold Ferrous near (but don’t touch them!) magnetic pickups to hear bass-heavy distorted beating of the magnets rotating. RPM also defines pitch of resulting sound.

12. When using Ferrous with exposed piano strings, the magnetic pull can cause the rotating disc to come into contact with the strings causing a loud buzz. This can also happen when the resonance builds to such a degree that the strings vibrate far outside of their normal bounds and contact the underside of the unit. A helpful method for stabilizing height is to slightly protrude the thumb and pointer finger past the flat bottom surface of Ferrous and rest them on the surrounding strings. This way the strings directly under the disc are left free to move. There are also 4 rubber feet that come with Ferrous. To attach them, remove one of the 4 silver screws place the rubber foot over the hole with the "cup" facing upwards and re-set the screw through it before moving onto the next screw/rubber foot.

13. Try adding the rubber bumpers (unscrewing one screw, place through rubber foot, and gently repeat 4 times making sure to secure each screw before moving onto the next screw). Now place the bumpered Ferrous atop a stringed instrument (making sure the bumpers are on the strings) and plug in a control voltage (0-9v) to control the speed with a voltage sequencer for example. You will hear the “slew” or ramping up and down of the RPM when there are changes in voltage between steps. Given the “ramping up” time to reach different steps, it could be useful to start with a slower BPM on your sequencer or modulation source in order to get a feel for this. Interesting results can be had with large jumps in voltage and small jumps. It depends upon many variables like what instrument it’s being used on, how the strings are tuned, how far apart the strings are, etc. It can be fun to utilize a keyboard that sends CV to “play” the notes and harmonics. To do so you’ll need to search for the notes on the keyboard that provide interesting RPM interactions for the strings that are under the disc. You many hear resonances build and “settle” into place that sounds somewhere in between a pitch bend and slow envelope attack.

12. *Use eye protection: Take two or more earth magnets and sandwich them around an object that is not easily resonated (a metal table leg, a cardboard box, a cymbal, a lamp shade, an aluminum bowl, a steel tank, etc.) and make sure that the poles of the magnets are facing the opposite direction to the magnetic disc before starting it up. Be careful of impacting the magnets with the disc (or any object for that matter) because it could send debris/particle/magnets flying!

-Ferrous' disc can move at very fast RPM. It's important to be careful of impacting the disc on objects that could be brittle.

-The disc has a textured design so be careful to not touch with fingernails or any item that could be scratched or damaged.

-Some guitar pickups (humbuckers for example) have lots of metal on them which could cause the disc to be magnetically pulled and impact the pickup, this could damage or demagnetize the pickup! Take caution. It should also be said to never touch Ferrous to any type of wound pickup to be safe.

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!