THX Deep Note (1982)

You’ve likely heard the Deep Note, the sound that accompanies the logo for Lucasfilm’s THX theatrical sound certification system. Created by Andy Moorer, it debuted in front of Return of the Jedi in 1983.

What you might not be aware of was that it was procedurally generated. Not only was it synthesized on Lucasfilm’s Sound Droid/Audio Signal Processor (a very early digital audio workstation), making it an example of computer music, but the instructions for the generation were output from a program written in C that created a list of parameters for the real-time synthesis. 

The program generated multiple versions, which let Moorer pick the version he preferred. It’s an example of Kasparov’s centaur, a human-machine collaboration. Procedural generation very frequently involves the human creator of the system nudging the result into shape. 

It’s also a good example of why it’s a good idea to store the seeds and parameters you use for your random generation. Since the random number generation of the original program was seeded with the time and date, when Lucasfilm temporarily lost the recording, it was difficult to recreate. (They got lucky and found a copy of the original recording.)

Recently, Andy Moorer recreated the sound for the new age of theatrical audio, starting from the same C code. You can listen to the result below, though the YouTube video does lack the ability to play the 9.1 version: