theremin tuning

Dear Thereminists--

I recently bought a Moog Etherwave Theremin which I am in love with. I've practiced countless hours on it, and have been making steady improvement (thanks to many of your tips here and on youtube). However, I have a technical question/problem: I get the pitch set up so that the intervals are the way I like them (open the hand comfortably wide for a 5th). But then during the playing of a piece the Theremin gradually changes, so now if I open my hands the same distance it is way more than a 5th. Then I have to reset the pitch to go back to what I would consider my "standard" setting--only to have it change again after a few minutes. Is this normal, and should I live with it, or can I do something to set it so that it stays where it should for longer than just a few minutes?

Many thanks!

Squiretron

It takes a little while (maybe 10 - 15 mins) for most theremins to "warm up". So if you tune and start playing straight after switching the theremin on, the note field will continue expanding for a while, and you'd need to retune.

The field can alter a little during lengthy practice sessions, and it would not be unusual to retune occasionally.

Other factors can effect the field, such as the distance you're standing from the theremin; if this alters, you might have to adjust the tuning a little.

However, if what you're experiencing is something more pronounced, and your theremin needs continual tuning every few minutes, this may not be right.

Squiretron,

I have always felt that a thereminist needs to be as fluid as the constantly shifting electromagnetic field in which we play. Efforts to concretize or standardize musical intervals so they correspond to certain thrusts of the fingers, or openings of the hand, are not IN MY OPINION the best way to play the instrument.

When we play the theremin we are not stepping from stone to stone over a pond. We are swimming.

I don't know what method you are using to play but it might help if you allowed yourself to be guided more by what you are hearing and less by fixed, memorized extensions of the hand and fingers (which are theoretically supposed to correspond to certain particular intervals).

The electromagnetic fields of all theremins vary depending on how long the instrument has been "on", ambient temperature and humidity, air pressure, slight changes in the power supply, all sorts of things. Only someone who is familiar with a properly functioning Etherwave could tell you if your theremin is performing within the acceptable parameters of variance, or if your instrument is in need of repair.

Most people are loathe to give up the technique they use to play the theremin even if that technique is putting them at a disadvantage. Attachment to even the most misguided method seems to get stronger with the amount of time spent practicing it.

Assuming your theremin is functioning correctly, if you are not happy with the results of your efforts so far, take a good look at the method you are using to play. Is it one of your own devising?

DON'T BE AFRAID TO START OVER. Nothing you have done so far will be wasted. Emulate, to the best of your ability, the approach and method of the thereminist whose playing you most enjoy until your own ideas and innovations naturally kick in.

Hi.
Could someone clarify me what all all the factors that affect theremin tuning? I've been playinf an Etherwave since last December and just got a new, more suitable amp. Before, I hadn't been playig anywhere else than my room and now that I'm trying to practice elsewhere, my Etherwave acts like a total bitch. (and this is where I get unclear because a)english is not my first language and b) I'm bad at explaining ) The tuning doesn't work at all like it should. Normally, when I stand about 30 cm away from the instrument, the note i hear should be about two octaves below middle C, right? Well, when I've moved my theremin to a different room, I hit zero beat when my hand is about at the edge of the theremin(=above knobs.) And at this point the pitch knob is at it's lowest(on the left).

I hope someone understood what my problem is. If so, PLEASE HELP.

[i]”Could someone clarify me what all all the factors that affect theremin tuning?” - vesiheinikki [/i]

ALL the factors? Would need to ask John and Jason to buy more storage for this site! ;-)

Some details here..
http://www.thereminworld.com/forum.asp?cmd=p&T=4837&F=780

[b]And a brief incomplete overview here:[/b]

The theremin operates by sensing capacitance between its “antenna’s” and ground..[b][ An "antenna" is, for LF theremin applications, a 'plate' of a capacitor AND NOTHING MORE - This 'plate' is capacitively 'coupled' to many other 'plates' which are all grounded (the room, wiring, etc) and to other 'plates' which are floating between the grounded plates and the antenna plate and have complex couplings - the player is one example of such a 'plate'... ][/b]

No explanation will be understood unless you understand [b]capacitance[/b] – so, if you don’t, Google it and understand it ..

Everything (Yes – EVERYTHING) affects capacitance – any conductive object placed between the antenna and ground (“in the field”) will give extra coupling between the antenna and ground (will increase the capacitance “seen” by the antenna) – and (to a much lesser extent unless one is talking about exotic dielectrics) non conductive objects like plastic, will reduce the capacitance “seen” by the antenna marginally.

The proximity of the antenna to ALL points in ALL directions, to any ground (or, for that matter, any conductive isolated object which is itself capacitively coupled to ground - as all such objects are..), will combine and add to capacitance “seen” by the antenna.. So changing the position of the theremin, changing the room, changing the wiring layout, changing the proximity of the amplifier or speaker/s or furniture, changing ANYTHING will change the tuning.

The dielectric constant of air also changes as a function of temperature and humidity..

Most changes are quite minor, and the tuning control is there for the purpose of compensating for normal “EXTERNAL” factors affecting tuning.

Giving a full answer to your question would require not only examination of these “EXTERNAL” factors (of which I have only scratched the surface in the above) but also examination of factors INTERNAL to the theremin.

In a well designed (and functional) theremin, the combined effect of all possible internal and external NORMAL conditions should not be so extreme that one cannot correct these conditions by tuning using the operators tuning control.

Internal factors include changes in component tolerances (particularly inductance values) as the result of temperature changes.

Some components age in a way which can affect tuning, and some components (particularly variable inductors) can go out of alignment mechanically.. This is why most theremins have internal adjustable components, so that, if required, they can be re-tuned by an engineer or knowledgeable owner.
But, in terms of understanding from a player’s perspective, IMHO a good understanding of CAPACITANCE is the starting point.. It is NOT an easy subject (easy enough to get some basic understanding, a lot more complex if one looks at it in depth – “full” understanding is not, I think, within anyone’s grasp – there are some gaps in our understanding of physics down at the quantum level which may be to blame ;-)

Fred.