The THX "Deep Note"

You have heard it in movie theaters -- the big swelling sound that advertises that the cinema has an authorized THX Sound System. Music Thing has a short writeup on the guy who wrote that and how it came into being:

"I like to say that the THX sound is the most widely-recognized piece of computer-generated music in the world," says Andy Moorer. "This may or may not be true, but it sounds cool!"

You can hear the sound here. It's called 'Deep Note'.

It was made by Dr James 'Andy' Moorer in 1982, who has had a very cool career: Four patents, one Oscar. In the '60s he was working in Artificial Intelligence at Stanford. In the '70s he was at IRCAM in Paris, working on speech synthesis and ballet. In the '80s he worked at the LucasFilm DroidWorks, before joining Steve Jobs at NeXT. Today, he consults, repairs old tube radios and plays banjo.

At one point, the THX sound was being played 4,000 times a day at cinemas around the world (that's once every 20 seconds).

The request?

He said he wanted "something that comes out of nowhere and gets really, really big!" I allowed as to how I figured I could do something like that.

And the synthesis technique?

"The score consists of a C program of about 20,000 lines of code. The output of this program is not the sound itself, but is the sequence of parameters that drives the oscillators on the ASP. That 20,000 lines of code produce about 250,000 lines of statements of the form "set frequency of oscillator X to Y Hertz".

"The oscillators were not simple - they had 1-pole smoothers on both amplitude and frequency. At the beginning, they form a cluster from 200 to 400 Hz. I randomly assigned and poked the frequencies so they drifted up and down in that range. At a certain time (where the producer assured me that the THX logo would start to come into view), I jammed the frequencies of the final chord into the smoothers and set the smoothing time for the time that I was told it would take for the logo to completely materialize on the screen. At the time the logo was supposed to be in full view, I set the smoothing times down to very low values so the frequencies would converge to the frequencies of the big chord (which had been typed in by hand - based on a 150-Hz root), but not converge so precisely that I would lose all the beats between oscillators. All followed by the fade-out. It took about 4 days to program and debug the thing. The sound was produced entirely in real-time on the ASP.

The ASP in question was a proprietary Audio Signal Processor that was eventually sold for scrap. Fascinating history for such a cultural icon.