mjn@teddy.UUCP (11/05/85)
I've been doing some thinking lately on non-keyboard controllers for
music synthesis (no doubt a common musing for some of you as well). I've
seen or tried such things as capacitance strips, PPC controls, breath
controllers, pedals, joysticks, etc. Another common control device is
to put a pickup on another instrument, such as guitar, drums, etc. I
had an intresting thought on another instrument to try as a controler,
which seems quite natural to me.
Many years ago (1930's ?) there was an instrument developed called the
theramin. This device sensed the position of the musician's hands in
relation to probe sets. These are usually set at right angles to
eachother. By moving your hands through the air, one could control a
VCO with one hand and a VCA with the other. AHA! This gadget is
nothing more than a crude synth in its own right!
Now suppose that we take the output of the positions sensors and use
them directly as control signals to a modern synthesizer. Better still,
convert the output to MIDI, channel selectable, so that it can be
integrated into a digital synth setup.
What does this give us? A modern theramin. One which can be programmed
for voices, one which can be used to control other parameters than merely
frequency or amplitude (filtering, harmonic content, feedback, noise, etc).
The theramin, once properly learned, can be an expressive instrument. It
was used to good effect in many of Led Zeppelin's albums.
One last thought. The original theramin used some sort of electromagnetic
field to sense hand position (capacitance? radar?). A more modern (and
probably cheaper) construction could involve distance or motion sensors
similar to the ones marketed by Polaroid. These are often used in
robotics to sense obstacles and walls in its path. These are ultrasonic
in nature, and may be more accurate that older methods. Anyone have ideas
on building such a thing?
--
Mark J. Norton
{decvax,linus,wjh12,mit-eddie,cbosgd,masscomp}!genrad!panda!mjn
mjn@sunspotins_adjb@jhunix.UUCP (Daniel Jay Barrett) (11/06/85)
> I've been doing some thinking lately on non-keyboard controllers for > music synthesis (no doubt a common musing for some of you as well). I've > seen or tried such things as capacitance strips, PPC controls, breath > controllers, pedals, joysticks, etc. > > Many years ago (1930's ?) there was an instrument developed called the > theramin. > -- > Mark J. Norton > {decvax,linus,wjh12,mit-eddie,cbosgd,masscomp}!genrad!panda!mjn > mjn@sunspot A modern Theramin exists! It is manufactured by Big Briar (Bob Moog, president. I have never used it, but periodically it is advertised in KEYBOARD. Dan Barrett
crandell@ut-sally.UUCP (Jim Crandell) (11/06/85)
In article <1586@teddy.UUCP> mjn@teddy.UUCP writes: >I've been doing some thinking lately on non-keyboard controllers for >music synthesis (no doubt a common musing for some of you as well). ... >Many years ago (1930's ?) there was an instrument developed called the >theramin. This device sensed the position of the musician's hands in >relation to probe sets. These are usually set at right angles to >eachother. By moving your hands through the air, one could control a >VCO with one hand and a VCA with the other.... >Now suppose that we take the output of the positions sensors and use >them directly as control signals to a modern synthesizer. Interesting idea, although I'd bet it's not new. Might be fun to play with. Personally, I can't get too enthused about the Theremin's expressive possibilities; I'd recommend that anyone who's seriously contemplating doing something like this try one before investing a lot of time and money in such a project. Of course, I'd be pretty short-sighted if I failed to admit the possibility that more sophisticated electronics could really turn the intstrument around. >One last thought. The original theramin used some sort of electromagnetic >field to sense hand position (capacitance? radar?). A more modern (and >probably cheaper) construction could involve distance or motion sensors >similar to the ones marketed by Polaroid. It would be extremely interesting to find anything so sophisticated in an electronic instrument of that vintage. Capacitance to sense hand position is exactly right. For pitch control, it consists of a metal rod (typically) wired to the hot side of the oscillator tank. A closer position of the hand increases the capacitance across the coil, lowering the frequency of the oscillator (this is NOT an audio oscillator, by the way. The audio signal is the lower AM product of the oscillator's output and that of an internal fixed oscillator). Since the body conducts RF signals nicely, the other hand serves conveniently as a plate of a capacitor coupling the signal into an amplifier -- closer position (more capacitance) means more volume (more coupling). I doubt anyone will find a cheaper way to do exactly the same thing today. If you want something cheap and dirty to experiment with, you might borrow an idea that showed up in Popular Electronics (of all places) some years ago -- use a pair of CdS or CdSe photo cells (you shade them varying amounts with your hands.) Naturally, linear control characteristics would be very difficult to achieve over reasonable distance ranges, and besides, everything changes with minor shifts in ambient lighting. Frankly, I wouldn't expect much of this scheme in a performance setting, but one might be able to get a feel for what could be done with better hardware. Anyway, the photoresistive cells give you analog (resistance) control signals to work with; what you do with them is your problem (but then, that's the easy part, right? [:-)]). -- Jim Crandell, C. S. Dept., The University of Texas at Austin {ihnp4,seismo,ctvax}!ut-sally!crandell
rich@aoa.UUCP (Rich Snow) (11/27/85)
In article <1586@teddy.UUCP> mjn@teddy.UUCP writes: >I've been doing some thinking lately on non-keyboard controllers for >music synthesis (no doubt a common musing for some of you as well). I've >Many years ago (1930's ?) there was an instrument developed called the >theramin. >By moving your hands through the air, one could control a >VCO with one hand and a VCA with the other. >The original theramin used some sort of electromagnetic >field to sense hand position. A more modern >construction could involve distance or motion sensors >similar to the ones marketed by Polaroid. These are often used in >robotics to sense obstacles and walls in its path. These are ultrasonic >in nature, and may be more accurate that older methods. Anyone have ideas >on building such a thing? > > Mark J. Norton > {decvax,linus,wjh12,mit-eddie,cbosgd,masscomp}!genrad!panda!mjn > mjn@sunspot We should be freed of keys and frets!!! Seriously... You might think more about how to work your triggering of the voice you use. The amplitude envelope is an important part of voicing (-and the Theramin sound). In some cases, when you select a voice on your synth it's going to be looking for a trigger for it's preset envelope rather than a changing voltage. Some sort of selectable threshold should work, or throw in a light beam & detector which dumps a pulse when broken. There was a designer's kit for the Polaroid sound circuit (prototype) which was being sold by the big P here in Cambridge. I can easily imagine a system with many sensors controlling varied parameters. (stick your hand in the path, move it until this or that parameter is changed, pull it out and have the system hold the last value) There's also a number of systems for "body tracking" which can provide coordinates of body members (digital). These are certainly more expensive but will be cheap sooner or later (now >5K). I am experimenting with one such system which will control a video sythesizer over long distance phone lines. This is much more crude than the digital music synths which you are talking about. The synth is analog (video synths mostly are yet) but will be controlled by the D/A'd tracking data. Such a mess! -luck in all ventures rich snow (-bbncca!aoa!rich)