Is it possible?

Is it possible to control the pitch through a keyboard attatchment?

Also, hi!

Yes. This could be done using pedals such as these: http://www.zzounds.com/item--DGTLIVE3 or http://www.ehx.com/products/voice-box; or by running the instrument through an audio programme with a plug-in like as Antares Auto-Tune set to MIDI mode. I imagine other methods could achieve similar effects. What is it you would like to achieve?

It is my understanding that theremin use radio waves to draw their tone and shapes the tone through the amp. I was wondering if there would be a way to controlling the incoming waves through a keyboard.

Also, that is one of the coolest things I have seen in a while.

Hi Zomniac -

It is not possible with any theremin presently on the market..

First question though, is why would you want to? The theremin is a theremin because it has theremin qualities (LOL) which include the control mechanism (non-contact capacitive coupling to the player) and its 'pitch freedom'..

As soon as you control it from a keyboard, you lose everything which makes a theremin a theremin!

If you want (for whatever reason) a heterodyning oscillator controlled by a keyboard, then this is possible - But I do not think there are any heterodyning VCO's on the market at present (I was hoping to put this product on the market in 2011-2012, but health has slowed me down or stopped me - and it would not be a high priority product anyway)

It is also possible to modify a theremin to control it from 1V/octave CV - But again, no-one does a kit for this, it was a product I was going to produce, and may yet produce, but probably not soon!

So - If you are into electronics, what you need to do is replace the antenna with an electronically controlled capacitance, take an audio feedback from the theremin, and create a circuit which takes a CV from the keyboard, and adjusts the capacitance so that the theremin produces the corresponding correct audio frequency.

Fred.

Fred, I hope your health has improved. The information that you gave me kicks most ass. I was worried that I would have to replicate an acoustic piano and replace hammers with small antennas.

The reason why I wanted to make a non-theremin theremin (a keymin if you will) is because I have an itch to make something and learn electronics.  Must.Scratch.Itch.

Also Thanks again for showing me those stomp boxes Charlie.

" I was worried that I would have to replicate an acoustic piano and replace hammers with small antennas"

LOL! - Now that would be quite a project!

If you want to play about with the idea, it should be quite simple to make a crude keyboard control for theremin pitch..

You want a keyboard (any electronic keyboard with contacts) and configure this to give a progressive voltage as keys are pressed (it will be monophonic, and you will need a trimmer to adjust the voltage from each key).

Take the keyboard voltage to a varicap diode circuit, so that the voltage controls the capacitance. Connect this varicap circuit between the antenna connection and ground (0V) (remove the antenna).

Adjust the trimmers to produce musical scale.

You can use a dual transistor opto-isolator instead of a varicap diode - connect the emitters together, the collectors become the connection to the variable capacitance - put a 47pF capacitor in series. Wire the LED's in series, use current through the LED's to control the capacitance.

The above circuits will drift like hell! To make a serious circuit, you will need to incorperate thermal compensation.. One way to thermally compensate the opto-isolator is to 'oven' it - Use a quad opto isolator, use one LED as a temperature sensor [LED1], and use one LED/Transistor pair as the 'oven' [LED2/Q2] (sadly, you cannot get quad opto-isolators where one has access to the transistor base connections) - Use the oven LED2 to control current through the oven transistor [Q2] so that it heats the chip up until the temperature monitored by LED1 reaches a value corresponding to about 40C*.. Use Q3 and Q4 as the capacitance, and LED3+LED4 to control the capacitance.

*You will need to put the opto-isolator into a controlled temperature environment ( container heated somewhere between 40C and 50C, or at least a temperature higher than it would ever see in normal operation ) - and measure the voltage drop across the LED at this temperature, so that you can set the correct value for the 'ovening' circuit .

Fred.

A series of metal rods, each reaching a different distance into the pitch field of a theremin. The player touches the end of each one. They are tuned by adjusting the depth that each one reaches into the field.

Disadvantage: Any movement of the player would throw them off tune. 

"A series of metal rods, each reaching a different distance into the pitch field of a theremin. The player touches the end of each one. They are tuned by adjusting the depth that each one reaches into the field."

Hi Gordon..

I seem to remember that we have been here before! LOL!

That idea wont work! - If all the rods are connected together, touching any of them (or increasing capacitive coupling to any of them) will be the same as connecting to all of them! - It will make absolutely no difference which one you touched!

But the idea behind your scheme is valid..

If one had a set of variable (trimmer) capacitors all connected together, with the 'open' ("antenna side") ends of these going to some sort of keyboard or panel (board with a load of drawing pins to which these presets are connected to the pins, and one touches the flat heads) one could then tune each for a different note.

Fred

This shows basic drawing-pin scheme, and alternative keyboard connection..

But beware! - Antenna lead is sensitive, trimmers are not stable, this will NOT make a reliable stable instrument!

The above has some big technical problems - main one is the trimmers - you would need to make these yourself with bits of insulated solid wire wrapped round each other.. the capacitive difference representing one semitone is tiny (<<< 1pF) and you cannot buy trimmers that small - your best bet is probably to have a circuit board (prototype board with copper rings or square pads, bit no tracks) and solder pieces of wire which can be moved with respect to each other to change the capacitance.

Zomniac said: Is it possible to control the pitch through a keyboard attachment?

I have no idea of what you are up to but theremin exploration is fun. Back in the day I tried to educate the masses with samples of my ideas, but they were viewed as having little creditability because I had limited math skills. They are all so silly. They just talk and talk and talk. (-'

This I think is what you want to do. It is pure theremin under strict control. Let the engineers tell you how it could be done!

Keyboard Precision .mp3 of a Theremin

Don't contact me, I am retired.