on octave dividing / Polysubbass

[Matthias Grob <matthias@grob.org>]

Basically there are two ways to do produce a lower octave:

- Either you divide every single wave (by switching the phase at 
every wave, usually) and such only achieve octaves, but totally 
regularly, IN PHASE with the original, so rather likely to colour the 
original.
This type cannot handle any multiple notes. Its usually done with 
analog electronics. It probably could be done better digitally, but I 
have never seen it in a multieffect.

- or you divide larger "sample" of the sound, with some complex 
algorithm. This gives the freedom to chose the pitch freely, but the 
resulting signal is not in phase and thus somehow apart from the 
original. Its a separate oscillation, so it rather sounds like a 
second string attacked together.
This type can handle multiple notes to some degree. The more harmonic 
the signal mixture, the smaller the glitches. This is only possible 
with digital electronics.

I designed the Polysubbass according to the first model, because I 
wanted to keep the original simplicity of the instrument and just 
give it the bass dimension. The idea came when Peter Gregor explained 
me that the success of the soft distorting Celestion type of guitar 
speaker was their subharmonic distortions. The material produces an 
octave effect. Since I wanted the guitar to sound good when connected 
directly to any good speaker or head phone, I had to add this sound.
To avoid the artefacts of string mixtures, it took an octaver/string. 
This not only avoids the interference "dirt", but reduces the pitch 
range of each octaver. With filters tuned to the strings, the 
tracking can be improved.
Also, I discovered, to fade out the bass effect shortly before it 
looses track, so I ended up without any artefact.
At last, I remembered that we never need two bass lines in a 
compositions because the interferences between low frequencies turn 
into inaudible vibrations. So I created the priority circuit that 
softly switches off one strings octave if a lower string is played, 
so when playing cords, you end up with just one clean bass note. This 
feature really extracts a bass line out of anything you play on the 
guitar - not even the VG8 does this.
For a rather natural low end enrichment, you can switch this priority 
feature off.

This lowest part of the frequency range is not reproduced by the 
"speaker simulator" units, which usually just treat the higher range 
with filters and dont add distortion as a speaker does. Since I dont 
feel like simulating anything, I did not emphasize this aspect of the 
Polysubbass.

Unfortunately, Polysubbass needs separate string signals to work, 
thats why we did not make big success with it. Maybe also because I 
did not show it the right way at the right time to the right people 
that could have manufactured it in their polyphonic guitar systems. 
Paradis pretends to reissue those products.
More about it: http://matthias.grob.org/pParad/Parad.htm

For my music, I never switch the Polysubbass off, its a part of my 
instrument. And I create all bass lines with it. For the really fat, 
ritch basses, I use the pitch shifter of the PCM80 in addition to go 
another octave down and get a parallel sound reminding of the several 
basses in the classical orchestra.

Have a listen to it on my music page 
http://matthias.grob.org/pMusic/CDsE.htm
As said, the effect is on all samples to some degree.
The samples with Marcio Miranda (lower part of the page) show the 
bass line side in a rather common ambience of keyboards and 
percussion.
On http://matthias.grob.org/pMusic/ppSound/MirFuncs.mp3 you hear a 
relaxed bass line. 
http://matthias.grob.org/pMusic/ppSound/MirSals.mp3 is a more 
agitated one.
On http://matthias.grob.org/pMusic/ppSound/MirPai.mp3 you hear it 
making the lower distorted notes fat.
On http://matthias.grob.org/pMusic/ppSound/ChinFin.mp3 you hear 
Polysubbass in a bass line fragment in the first part and a fat bass 
with PCM80 in the second part. Mind that its the final part of a 25' 
piece.
On http://matthias.grob.org/pMusic/ppSound/RioProf.mp3, there is also 
the PCM80, very heavy.
Mind also, that all this music is improvised and mixed live with only 
one loop unit!
This reminds me that I should record what I do now...
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