Okay, I was under the impression that PDM worked in a similar way to motor control with PWM, where a particular cycle of your pulse signal has a Vrms = Vm*sqrt(Duty). As you keep changing the width of the pulses, the Vrms changes, and if you smooth this waveform, you get an analog signal encoded by the varying pulse widths where each "point" of your final waveform is equal to the Vrms of the pulse cycle that created that "point."
Clearly, there is something I'm missing. I know this, and it's why I started this thread to begin with.
Now, with PDM, you have a ton of pulses moving by. If you have, say, 1010, you have a square wave of two cycles, but any number of ones and zeroes can be next to each other: 11101110 - this is equivalent to two cycles of a 75% duty cycle pulse. So it seems to me that PDM is almost the same as PWM, the difference being that the frequency of pulses is fixed, rather than the frequency of any particular waveform that results from a train of pulses. I really hope I'm explaining what I'm seeing in my head good enough here.
I really don't know if that makes any sense. It also doesn't look like my oscillator idea is going to work, not just with simple logic chips. My ultimate dream was to design an analog (or sort of hybrid analog/digital) discrete-time modular synthesis "computer" of sorts, where generic function blocks can be configured to accomplish different tasks, like filtering, oscillation of arbitrary waveshapes, and creating control signals. PDM really looks like a way to accomplish this.