This is how I picture it, and I may be wrong.
Imagine a piece of string attached from both sides, now add an LFO to make that string oscillate. The LFO doesn't have to be a simple wave (sine, square, saw, etc.) it has physics principles that allow it to have a user-defined life for a certain amount of time. Same as a guitar string, but with unlimited oscillating options. So, you can make the string be plucked at the center, and take X amount of time to die out, or that the string is very tight but a big plucking force is applied thus dying out quickly with a fast attack. Maybe this could be compared to a physics engine for string? And have a sort of ADSR type evolution?
The scanning part, I think is how the pitch is controlled. So if the above gets scanned periodically at 440 times per second, then the frequency will be 440Hz.
Now if you have control over the shape of the oscillation (timbre), and have a separate control over the speed of the scanning (pitch). You have a system that allows you to control the timbre and the pitch separately.
Basically, you can use this to build a string vibrating physics model.
I found this video, check from 40 sec onwards, it explains well: