Deep Note is the name of THX's audio logo, a distinctive synthesized crescendo sound. It was created by Dr. James A. Moorer, then an employee of the Lucasfilm Computer Division, in 1983. The sound is used on trailers for THX-certified movie theatres and video releases; it debuted in the THX trailer shown before the 1983 premiere of Return of the Jedi in Los Angeles.
The U.S. trademark registration for the sound contains this description of it:
The THX logo theme consists of 30 voices over seven measures, starting in a narrow range, 200 to 400 Hz, and slowly diverting to preselected pitches encompassing three octaves. The 30 voices begin at pitches between 200 Hz and 400 Hz and arrive at pre-selected pitches spanning three octaves by the fourth measure. The highest pitch is slightly detuned while there are double the number of voices of the lowest two pitches.
While the Deep Note had originally been from a soft to loud pitch from its debut in 1983, the Deep Note over the years has been remixed digitally, with then-new technology, which made the Deep Note with a more abridged sound. Beginning notably in 1988 the Deep Note became louder and abridged, and in 1993 the Deep Note was cut short to save time for Laserdisc (1995 for VHS). Most recently, however, the Deep Note has been cut short to the single note (where both sounds stay in one pitch), in favor of other sound effects in certain THX logos.
The sound is perceived as louder than it actually is; sound designer Gary Rydstrom explains that, "from a technical standpoint, 'Deep Note' just feels loud because it has a spectrum of frequencies that grows from small to large."
James A. Moorer has been quoted as saying, "I like to say that the THX sound is the most widely-recognized piece of computer-generated music in the world. This may or may not be true, but it sounds cool!"
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 Audio Signal Processor (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".
Prior to the creation of Deep Note, several other works made use of similar techniques of frequency spread.
In their book Analog Days, Trevor Pinch and Frank Trocco point to the track "Spaced," from the 1970 Beaver & Krause album In a Wild Sanctuary as the source for Deep Note. They quote synthesizer builder Tom Oberheim as saying the original analog form is much richer than the "digital perfection" used in movie theatres.
Asia used Deep Note as the opening for the song "Countdown to Zero" from their 1985 album Astra. In 2000, Rapper Dr. Dre was sued by Lucasfilm, then-owner of THX, for using an unauthorized sample of Deep Note on his album 2001. The sample is used at the very beginning of his intro song and is almost entirely unedited and played in full.
- Moorer, James A. "James A. Moorer Personal Website". Retrieved 2006-12-03.
- THX Ltd. "THX Trailers". Retrieved 2006-12-03.
- "Trademark Applications and Registrations Retrieval (TARR)". United States Patent and Trademark Office. Retrieved 2006-12-03.
- Whitwell, Tom (2005-05-25). "TINY MUSIC MAKERS: Pt 3: The THX Sound". Music Thing. Retrieved 2006-12-03.
- Dansby, Andrew (2000-04-21). "LucasFilm (sic) Taking Dr. Dre to Court". Rolling Stone. Retrieved 2006-12-03.