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Thunder and Explosions

In the last issue of POLYPHONY, there was a letter from Dale Naylor requesting thunder-type patches. In response to his request, several readers sent patches they had used to create thunder and explosions (a close relative of thunder). Since there seems to be considerable interest in these types of sounds, we decided to present several thunder patches for your evaluation.

The first response we received was from Hank Jones of Mesquite, Texas. He suggested using a reverb module whose output was connected to an amp., but with no input applied. Make sure that the external amp is at a low setting (due to the high output level which will be produced) and gently shake the cabinet which houses the reverb spring unit. The induced vibration of the springs will cause a decaying rumble similar to thunder. If you have the spring can mounted such that you have access to the actual springs, a different sound can be achieved by rubbing the springs with a finger or other object.

A short time later, we received a contribution from Allen Fairfield of Wakefield, Mass. His patch was entitled "Galactic Explosion", but as he pointed out, it could be converted to thunder by extending the envelope attack time. Allen's complete patch can be found in the Dear PAIA section.

When I realized that there were a number of people interested in these types of sounds, I decided to do some work in our studio concerning subharmonics and sub audio signal generation. In the process, I developed a very interesting patch. But, before talking about the patch, there are some inportant points that must be covered concerning amplification. The frequencies produced by this patch are very low — mostly below audibility. The resulting effect is similar to the "Sensurround" effect in the Earthquake movies, in that we are dealing with considerable air motion to create a physical feeling rather than an audible sound. Consequently, considerable amplifier power and speaker response are required to get the "earth shaking" effect. This doesn't mean that you have to go out and buy a stack of Phase Linears and Cerwin-Vega speakers. It simply means to make sure your system can handle the signal. Low frequencies always use more amplifier power than an equal amplitude high frequency, and low frequencies at high power cause tremendous woofer excursions.

The subsonic patch is shown on the facing page with comments for setting the various modules.

As mentioned in the comments, make sure that all VCO's are tuned to minimum, and that no two VCO's are tuned together. A properly set 4730 Filter will pass only frequencies below 30 to 40 Hz., and what you hear will be a combination of the beat frequencies created by the mistimed oscillators and mistimed fundamental frequencies of the more complex VCO outputs. No VGA is required due to the cut-off frequency of the 4730 going far below the lowest frequency we will be using. This patch is a lot of fun and is great for freaking people out.

P. S. - After you've done the thunder, try this: Turn the keyboard pitch control to maximum. Leave the VCO's mistimed. Set the ADSR Attack and Release controls to 25%, and set the 4730 range control to maximum (leave the High/Low switch at low). Press the second C from the top of the keyboard and you've got a diesel truck horn!



Keyboard - Set pitch at minimum and press lowest C for thunder.
Transposer - Set all controls to minimum, but check to make sure that no two VCO's are at the same frequency.
VCO - Use square wave outputs.
ADSR - Attack - 50%
Decay - Minimum
Sustain - Maximum
Release - Maximum
Mixer - All inputs mixed equally with maximum amplitude.
4730 - Low-pass output, Range switch - Low
Initial frequency - 50%
Sweep switch position
Q - 50% or less.

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A Totally Synthesized Recording

Polyphony - Copyright: Polyphony Publishing Company


Polyphony - Apr 1976

Donated & scanned by: Retro Synth Ads


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