Here it is after swapping all the resistors and capacitors in the previous design, I did not get any results. I might had a radical change of design earlier which involved many trial and error. Sadly, back then I hadn't got any oscilloscope or signal generators (was a college student many years back) and seeing what was going on was almost impossible. Even with my new Analog Discovery 2, this arrangement did not work at all! There must be some way to generate a simple envelope in a simple manner without using too many components.

However, I'm wrong - I may need an op-amp, a transistor and two diodes to make this all happen. I'm not sure if the authors at the PICBasic tested the design, but let's not brood over other's problems for now. I'm here to improve whatever it is on the page, and this time it will be good!