all about expression pedals

All about expression pedals

Expression pedal database and how they work

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Black Magic Motion

What makes this device interesting is

  • the unique way it achieves expression
  • the large range of expression features
  • the sounds made possible through software control & movement dynamics
  • true universal connectivity and compatibility, including control voltage and variable resistance

Black Magic Motion from Oz Inventions, is made up of two devices. A sensor/transmitter which acts a bit like a traditional pedal and a receiver/modulator unit that connects to a foot controller port on an effects pedal, keyboard or MIDI device. The sensor has an accelerometer in it that senses acceleration and a gyroscope to sense angular velocity. The acceleration and gyroscope data is sent wirelessly to the receiver where it is decoded in software and used to control the resistance of a digital potentiometer.  Just like a traditional pedal, the digital potentiometer is connected to the control port on an effects unit.

Essentially as the sensor is moved about an effect parameter is moved. However, it has a heap of different features to enhance the expression and seems to be absolutely universal and even includes a control voltage output. There are models with MIDI output also that enable it to function as a MIDI controller.

There are a stack of inbuilt features that enable it to do some truly unique things.

There is a built in ADSR wave shaper. It can be set to run automatically, or can be triggered by moving the sensor. The ADSR is fully adjustable with rates for attack, decay, sustain, release and an overall rate. When set to trigger mode it can be set to repeat continuously or to play just a single time.

The motion of the sensor can be recorded and then played back to create your own oscillation pattern

The receiver can be turned on and off with a foot switch but it can also be set to turn off remotely by flicking the sensor. There is a sensitivity control to adjust this.

There are all sorts of sweep options. Reverse, bi-directional, quad-directional. linear, log and anti-log

Both the minimum and maximum depth can be set. So, for example a Wah effect can be set so that only the sweet spot is accessible so there is no muddy bottom end or ear grating top end. The maximum depth could also be used on a pitch effect to set the musical interval risen to.

The sweep is generally smooth with individual steps from 1 - 127. However, you can set this to jump in steps of 2, 3, 4 .... 127. So, the changes can be made quite lumpy or to act like an on/off switch

There is an option to set custom step sizes. So, for example the first step could be 20, then the next 25, then 60 then 30 etc. You can get some pretty unusual effects with this, and for an effect parameter like pitch, you can set musical intervals.

The output can be changed in the internal menus to have 10kohm compatibility, 25kohms or 50kohms. Actually the  10kohm option is really 12kohms but is compatible with all 10kohm devices. The polarity can also be changed between TRS, RTS, TS and even CV (control voltage). The control voltage goes from 0 - 4.8 volts which gives a fair range on control voltage devices like analog synthesizers.



The sensor has various methods of attachment. Double sided hook and loop tape can attach it to most things. A hook and loop elastic strap attaches to cylindrical objects such as an arm, leg or guitar neck.

Movement along or around an axis will modulate an effect parameter in the following modes -

  • Force
  • Speed
  • Rotation (yaw)
  • Tilt / Roll
  • Guitar-Hand (a different type of rotation)

Each of these modes replicates the modulation effect of the heel to toe motion of a traditional expression pedal.

Pitch, roll and yaw are commonly referred to as X, Y and Z respectively. Pitch (X) is tilting the device up and down on the slotted side. Roll (Y) is tilting the device side to side on the short side. Yaw (Z) is turning the device left or right . Speed is rotation around an axis. Force is sensed along an axis

It is a very interesting pedal that does some wonderful and also some weird stuff. The menu system was a bit tricky to use, but the features in it are really unique and it seems to work with everything out there.