Re: good feedback vs. bad feedback,or the revenge of the 10 dollar microphone.

[Richard Zvonar <zvonar@zvonar.com>]

At 6:07 PM -0500 3/20/01, LEE, THANIEL I wrote:
>has anybody here ever tried to record a record using nothing but 
>microphone
>noises and feedback. well i am attempting to do so and im wondering if
>anyone has any sugestions. i like the cold organic tones of feed back and
>the clicking sound made when the mic gets pluged in or ajusted. i already
>have one track done its a 25min drone/click/pop/hiss/pulseing epic its
>called [one] -thaniel ion lee

The behavior and tonal characteristics of feedback are dependent such 
things as the resonant characteristics of the acoustic (or virtual 
acoustic) space it inhabits and the transfer functions of the 
transducers the signal passes through. You can play around with the 
use of different microphones, different loudspeakers, different 
rooms, and the use of filters, reverbs, and other signal processors. 
It's interesting to set up a sound system with multiple microphones 
and multiple speakers in a naturally reverberant space and then play 
around with the mixer levels. You can do a similar thing by 
crosscoupling feedback paths within a mixer but substituting multiple 
reverb units for the physcial room.

I did some interesting work a while back with feedback and a 
Fairlight Voicetracker pitch-to-MIDI convertor. A microphone fed the 
Voicetracker and the Voicetracker controlled a synthesizer. The 
synthesizer sound was fed through a digital reverb with a rather long 
decay time and that was fed into the room through a set of 
loudspeakers. Because the reverb time was long, there was a 
phenomenon I call "resonance memory" - certain pitch resonances would 
build up in the reverb and be detected by the Voicetracker. If 
several different pitches were sounding at once, then Voicetracker 
would jump from one to another in often interesting ways. The first 
piece I did like this used one hand held microphone. I initiated the 
process by making one short vocal sound into the mic and then I waved 
the mic slowly through the speaker's sound field. I did several 
passes, with different synthesizer sounds on each track, so there was 
a kind of organic growth process as each new track added to the 
source material for the Voicetracker process.

I also worked with acoustic instrumentalists and a singer, using 
several mics sent via the mixer's aux send to the Voicetracker. The 
main signal "heard" by the Voicetracker came from whichever 
instrument or voice was being fed to it at the time, but there was 
also some bleed-through of the reverberated synthesizer sound. One 
particularly interesting effect came from miking a marimba with two 
mics. The percussionist played sustained tremolos and varied the 
harmonic intervals. This generated some interesting arpeggiations. 
Another interesting effect came from solo bassoon. This instrument 
can often "lose" its fundamental frequency, with most of the timbre 
coming from the overtones. The player could control these timbral 
changes and achieved a fine degree of control over the response of 
the Voicetracker.


I realize these pitch-to-MIDI techniques are somewhat removed from 
your initial query about feedback, but there IS a certain conceptual 
and physical acoustics commonality.


Also, on feedback music:  I recall that a few years ago Neil Young 
did a limited edition CD compilation of guitar feedback from live 
gigs.
-- 

______________________________________________________________
Richard Zvonar, PhD                     zvonar@zvonar.com
(818) 788-2202 voice                    zvonar@LCSaudio.com
(818) 788-2203 fax                      zvonar@well.com

                 http://www.zvonar.com