Multiple Theremins with 1 Hand

Hi...
i am new to Theremin World and i have some important Questions. I am working on a project where i want to set up 3 theremin Antennas in a coordinate System.

Does someone know if it is possible to steer more than 1 Theremin with only one Hand, or will they always disturb the other.
Maybe using a differnt frequence on the other Theremin?

maybe someone can help me...thx

[i]"Does someone know if it is possible to steer more than 1 Theremin with only one Hand, or will they always disturb the other.
Maybe using a differnt frequence on the other Theremin?" [/i]

Hi, and welcome to TW!

What you are wanting is possible - but not simple! IBM spent a lot of R+D on their "E-Field mouse" http://seattle.intel-research.net/~jrsmith/fieldmouse.pdf and Musical Applications of Electric Field Sensing (http://phm.cba.mit.edu/papers/98.02.CGA_Final.pdf) is a MIT article which covers also discusses this.

I have been working on (and now have a functional prototype going into production as soon as I have field-tested it) a 3d "E-Joystick" - and this has taken me the better part of a year to get right.

I can give you a few tips, but cannot give away my secrets (or at least, not unless you were looking at marketing these and willing to enter into an agreement with me) but can give you some clues.. These are based on my expierience - if I say "you cannot" or things like that, these are my assessments only - I could be wrong!

1.) You cannot use a "multi - theremin" design - frequency interactions become too complex to manage.

2.) You can use a single VFO (Variable Frequency Oscillator) and multiplex this across several sensing plates - this works quite well if one manages the timing with a MCU.. My Epsilon (http://www.therasynth.com/home/) controller used this principle.. [i](this project was abandoned for many reasons - including the fact that control of pitch and dynamics with a single hand is IMO unworkable.. and also due to complexity / cost etc.. The E-JS is an analogue derivative of Epsilon which overcomes the problems - but is not intended for control of pitch - it is intended for dynamics / effects and vocal formant synthesis)[/i] the oscillator running at 500kHz with ~3kHz deviance, and being multiplexed every 250us, giving a 1ms total update time.

3.) You can use a fixed frequency oscillator driving all the sensors, and use RLC circuits on each sensor such that change in the capacitance on any sensor changes the resonance of the RLC - one then rectifies the outputs from each sensor in a similar way to that used in the volume circuit of most theremins.

When you have the raw data from any of the above schemes (or from the scheme I have not told you about ;-) you are just at the beginning of the process..

You have (say) 4 values relating to the outputs from 4 sensors - these values need to be scaled, 'equalized' and computed to provide the required output, which is positional data.. In my case, I resolve this to an X value which gives a voltage for left-right hand movement, a Y value which gives a voltage for Forward/backward hand movement, and a Z value which gives a voltage for Up/Down hand movement (Strangely, this one is the most difficult to get linear).

My E-JS boards should be available soon.. Had hoped to have them on sale this year, but boards which should have arrived two weeks ago got lost, so it will be Jan / Feb now before I can "roll" them.. Contact me if you want to be kept updated.

Fred.

The other issue is hand control. Even with very well structured, stable fields, there is the challenge of playing three notes at once - if that is your intention. This sounds at least three times as challenging as learning to play a single note instrument, which is already a skill that takes a good deal of work to acquire and maintain. Probably more so.

So it is fair to assume that melodic and harmonic playing is not your intention. If that is the case, how much field instability - i.e. unpredictability in both pitch and timbre - would be acceptable for your requirements as part of a metal band?

Playing two etherwaves together produces a pretty raw sound and a lot of strange field behaviour, and three instruments with similar or related tunings would be even more so. As Fred noted, without a far more complex approach this would be very difficult to avoid.

But it would be fairly straight forward to produce something which is sonically interesting from it, if not necessarily predictable or harmonious, with further processing, giving you a rhythmic or drone instrument rather than a melodic one - by processing the sound further via effects.

It will remain an instrument in which you can develop skills to get the best out of it, albeit a different skill set to that of a classical thereminist.

[i]"Even with very well structured, stable fields, there is the challenge of playing three notes at once - if that is your intention. This sounds at least three times as challenging as learning to play a single note instrument, which is already a skill that takes a good deal of work to acquire and maintain. Probably more so." - Gordon [/i]

I believe the complexity is likely to be a "raising to the power of" type relationship.. Playing 2 antennas being = 2*2 (4 times harder) and 3 antennas being 3*3 (9 times harder).. But I have not formed a mathematical proof of this hypothesis yet, LOL! ;-)

Having a split vertical antenna driving two sound generators is the closest I have come to playing with polyphony - keep the hand aligned to the centre (vertically) and both oscillators are at the same pitch, raising the hand increases pitch / lowering hand decreasing pitch of the other oscillator.. Ok, prototypes were far from perfect (pitch of one oscillator dips slightly as other increases) but even if perfect, I think playing two voices accurately will be a huge challenge - at least 4 times more difficult than playing one voice.

I suspect the question was more related to control of something other than pitch - perhaps something even un-related to music.. (flying a helecopter, or playing Mario.. ;-)

For pitch control, I do not think one could use even two normal theremins and play them in a controlled manner with one hand - it is simply impossible to control the pitch of one without influencing the pitch of the other - and there is no possible antenna placement which allows one to cover even a couple of octaves (or for that matter, any span) and would allow the player to select the required related pitches.. the positions for all multiple note combinations simply would not exist in the E-Field.

I think that duo-phony is as polyphonic as a theremin could ever be - unless one was to have preset chords located in the E-field (for example on the vertical axis).

Fred

I said:

[i]"and there is no possible antenna placement which allows one to cover even a couple of octaves (or for that matter, any span) and would allow the player to select the required related pitches.. the positions for all multiple note combinations simply would not exist in the E-Field."[/i]

I think I was theoretically wrong here..

If one places the theremins apart by a distance such that the null-point of each theremin is located at the other theremins antenna, then one has a control field consisting of an equilateral triangle (a,b,c where ab is the line between antennas, and when ac = bc [c being players hand position] both theremins are at null)

At any position within this triangle, (except when c is located within line ab, in which case the 'triangle' becomes a straight line and any point on this line results in a predictable pitch change on both theremins, but no possibility of independently controlling these pitches) there is some degree of independence. (well - not actually independence.. but the ability to control pitch of each intentionally, to a limited degree, rather than being stuck to "if I go up one semitone on a, I must go down 1 semitone on b" as one is in the zone directly between antennas)

The further c gets from the line ab, the more independent control of the pitch for each theremin becomes available.

I think my above hypothesis is correct. It would be great if some mathemajician would comment!

Fred.

Edit -> I think the triangle idea is wrong.. it would be two circles drawn 'round the antennas, with radius equal to null-point distance, radii being equal length and this length being the distance between theremin antenae.

The 'play zone' where one could control both theremins would be the areas where the circles overlap.. I think the general idea about freedom or 'independence' being greater as one gets further from the zone between the antennas, is still true.