Emergent theremin like control in a bent alarm?

[obs]

I recently circuit bent a little safety alarm type thing that colleges give out to freshmen. its a very simple circuit with an oscillator and some sort of modulation to produce a very irritating siren.

I found some interesting bends, although nothing special. After i cut off the speaker, a piezo transducer, a soldering a jack in, the siren is behaving very differently than before (because of extra energy in the circuit??)

It's now very aleatoric, but also it can be controlled in pitch and texture by the position of hands and objects near the circuit board. I assume this is because of electromagnetic interference or something, but i really have no idea.

Has anyone encountered behavior like this before?

[electri-fire]

I have no experience with this myself. Let's try find an explanation.

(quote)

Piezoelectric elements are essentially capacitors. Their internal resistance is in the order of 100.000 M. Consequently, under static operation virtually no current is drawn nor power consumed to maintain a state of activation. Power is only required to change the voltage on the piezo element.

source: http://www.noliac.com/Material_characteristics_-143.aspx

I suspect replacement with an output draws more current from the circuit, thus starving the circuit or something. Aleatronic behavior sounds cool, but those that want to avoid it might insert a resistor between the circuit and the output. I don't think this would need to be as high as 100.000 M.

Do you have enough output level or just barely?

Also (edit: First Of All) as the piezo transducer is a capacitor, it works as a high pass filter. Without it low frequency oscillations might influence the circuit.

Inserting a capacitor may reduce these. Maybe 0.1 uF , or larger to retain some more lows. (0.1 uF is used often, but too small for my taste).

Edit:

Oops, a capacitor already blocks current flow doesn't it? No resistor needed then.

So, concluding: (based on my resticted notions of theory)

-When bending a circuit with a piezo transducer, it's best to FIRST make your output jack. Else your meticulously finetuned bends may not be as finetuned as you anticipated.
-When you want more stability, insert a capacitor before the output.
-A relatively boring circuit may turn into a fine random noise instrument when starved of voltage or current.

Thank you for posting your experience, we may have learned something. More comments are welcomed as usual.

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