What's more important for sound?

Bass shape: 60Hz, 150Hz, 330Hz

I guess - concern all what you has shown - that your pitch and volume parts are well. The more quadratic form in the lower register is probably due to RC filtering effects, whos time constant influences higher audio frequencies more than the lower ones. Try to enhance the coupling capacitors in the a.f. part of volume control and you will see an effect. 

But the loudspeaker signal is really complete wrong. May be there is a problem of shielding (pitch antenna has a couple of 100 volts r.f., straying in the circuit) into the audio amplifier / buffer unit. Also a wrong grounding or incorrect mass conections could be taken into account. Hope this recommendations are not too annoying, but without more knowledge of the concrete situation it is not easy to give more help. 

innominata, you have an audio amplifier of some sort driving the speaker, correct?

innominata, you have an audio amplifier of some sort driving the speaker, correct?

I want to say no. The signal train is Mixer -> VCA -> PushPull -> Speaker.

Have you tried hooking the VCA output to an external amplifier & speaker (like a stereo, PA, guitar amp, etc.) ?

Also, driving anything significant off of the Theremin power supply can be problematic from a voltage regulation standpoint.  The oscillators can be quite sensitive to voltage variation.

When the car is not going - first look at the engine and transmission, and last of all at the wheels. You can connect the speaker to another source for verification: radio, amplifier, or CD player... It's probably working. You compared the sound to site Christopher's sound. Are you working on this design?

When the car is not going - first look at the engine and transmission, and last of all at the wheels. You can connect the speaker to another source for verification: radio, amplifier, or CD player... It's probably working. You compared the sound to site Christopher's sound. Are you working on this design?

No I'm working on my own design.

Today, this information paradise is simply left out of the picture. I have noticed that the global network is growing by leaps and bounds, and with it, the amount of information available is increasing. A huge number of video, audio, and visual files are freely available every day, willy-nilly. But does this mean that we can use these files to our advantage? That's why I would recommend using a noise effect - that background soundtrack, like free stock sound effects - that will set the rhythm and feeling of fullness to your music.