Pea Soup

Pea soup was one of if not the first self-stabilising feedback systems developed by Nicolas Collins. In doing so the uncontrollable loud feedback we all should know, was tamed into tones that are a product of the environment they are in. Nicolas Collins describes this phenomenon as an 'Architectural Raga' and it is a good comparison, you can really get a sense of it as the resonances of the room are plucked from the silence in the air.

Some of the essentials that are still used in feedback music today were laid out by Nicolas Collins:

• Phase delay changes feedback frequency by emulating physical movement of the microphone.
  
• A limiter controls feedback and transforms a shriek into a mellow sine wave.
  
• Omnidirectional microphones (especially dynamic ones) produce more controllable feedback than cardioid mikes.
   Taken From Pea Soup - A History

Collins goes into great depth about the Countryman 968 phase shifter, this was a fairly unique item in that the delay time could be controlled by the amount of input level from another source, meaning that as level increased so too would the delay time resulting in the wavelength being lengthened at thus causing a different frequency of feedback to occur. This will be covered in more detail in a later post.

Below is the patch diagram for the original incarnation Pea Soup.

Pea Soup patch diagram (1976) 

As can be seen it is fairly simple in set up but the results can be spectacular, especially as the slightest movement or noise in the room can cause the system to behave in different ways, inherently linking performer, audience and room. 

However, as Collins quickly discovered if only a single microphone and speaker were used the feedback would only drift between two frequencies. When adding another duplicate of the pea soup patch they would begin to interact. The inherent linking of all the components of the system is fascinating and the dependance on the architecture makes it a truly fascinating listen.

Have a listen here.