2. Amp Envelope: loooong Release, so that the sound keeps going after you let go of the keys. And if your envelope’s release stage has a curve control, curve it upwards so that it hangs out at the top for most of the release. This will give the impression that it’s ringing out indefinitely.
3. Pitch Envelope. Routed to the Oscillator’s pitch. The amount should be enough to raise the pitch up one octave at the top of the Attack stage. Set the Sustain to 0, and both Decay and Release to about 590 ms. And then the key to getting this sounding just right is the Decay and Release stage curves. In Serum’s case I had to raise both curves up until they were a little above being a straight line. This will make the note hang out a little bit longer near the top so you can hear that higher octave, and then swoop down.