Coming a bit late to this, but I'd say the high pitched noise is a resonating synth filter with high resonance, which creates a sine wave. This is then passed through either a chorus and delay or a modulated delay, then reverb which is also possibly modulated.
The filter frequency can also be modulated, including by an LFO, sometimes with a frequency that's in the audio range to create a kind of FM synthesis. Sometimes a little noise needs to be fed into the filter to get it resonating or to broaden the sound a bit. Then you smoothly slide the filter frequency around.
At least, that's been the 'industry standard' way of getting that effect for the last 40 years or so. The synths of choice being pretty much anything, preferably analogue, with a self-resonating/oscillating filter. VCS, Moog, Korg, ARP, etc. A Korg Monotron is a very cheap way to get that kind of sound and it does it very, very well, just get the standard model, not the one with delay built in as that lacks the necessary resonance control.