I always thought the THX sound was a cheesy rip-off of the opening from legendary Blues guitarist Gary Moore (RIP), to "Nuclear Attack", "Dirty Fingers" album recorded in '81. [0]
to synthesize it in real time, in 1983,
took 2 years to design and build a 19”
rack full of digital hardware and 200,000
lines of system code to run the synthesizer. [1]
Creating sound using DSP is hard so you need somewhere to start. Is this Gary Moore track the start point? Make up your own mind.
The Gary Moore sound is a simple pitch-down of a single (rich) synth patch. There are no rising harmonics in it. Further, it wasn't actually released until '83 at the earliest.
The Deep Note uses a whole bunch of cello patches, each following its own pitch envelope, and resolving on the final 5th. IIRC Moorer generated a large number of versions to demo (as it used a random initial starting sound) and the winning version just happened to have a bunch of voices start on a similar pitch shifting down.
Listen to the sound here ~ https://youtu.be/5XpKaitVy_E?t=19m8s You can see a live version in '83 with the synthesiser in action here (Pinkpop Holland 23.5.1983) ~ https://www.youtube.com/watch?v=IIw4RqENjDc
Creating sound using DSP is hard so you need somewhere to start. Is this Gary Moore track the start point? Make up your own mind.Reference
[0] https://en.wikipedia.org/wiki/Dirty_Fingers
[1] https://en.wikipedia.org/wiki/Deep_Note