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Adding pitch-CV together what do you get?
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Adding pitch-CV together what do you get?
tedcri
I am playing around with two A-185-2 precision adders (euro).
I have two quantized sequencers going into one of them.

The logic i just need to understand is: Lets say both sequencers are quantized to "blues" but playing completely different sequences both in notes and time. The sum of both sequencers goes trough the adder and into 1 oscillator.

What am i getting into my Pitch CV in on my oscillator? Will it still be blues scale notes? Or can it be anything because the different voltages when added can add up to anything?

Or does the pre quantize mean something at the end of the chain and limits the notes to just "blues" notes?
Navs
Interesting question. I know stuff all about scales, but as you say, it's just simple addition, i.e. maths. Have you tried it?

If you want to ensure that the output is 'correct', why not mix the two sequences before feeding them to a single quantizer and then on to the VCO?
Joe.
tedcri wrote:
What am i getting into my Pitch CV in on my oscillator? Will it still be blues scale notes? Or can it be anything because the different voltages when added can add up to anything?


It can be anything, and it will be extremely high pitched (unless you offset it)
cptnal
My gut feeling on whether your output will fit the scale of your input is "not necessarily", but you'd probably have to write a Python script or something to actually prove it. Back of a fag packet at least. hmmm.....

Navs' answer about quantizing post-adding is what I'd do (unless you actually want the unpredictability).
Jay F.
You received already good advices.

To add some precision (pun intended !), just like voltage is a difference between two potentials, pitch control voltage gives an note interval. At 1V/oct, you have 83.3 mV / semitone (a full tone is 166.6 mV, minor third is 250 mV, fifth is 583 mV, octave is 1V hopefully).

I sometimes saw 0V being referenced as a C or an A. But I'm no expert.

What you are doing is transposing your blues scale given by one of the sequence to a key which root note is given by the other. And vice-versa.
The end result is not necessarily in a coherent key.
authorless
The blues scale would:

Root, one and a half, whole, half, half, one and a half, whole

And in steps relative to root:

0, 1.5, 2.5, 3, 3.5, 5, 6

When you add those together, say the third note in the scale (two and a half steps above root) and fourth note in the scale (three steps above root) you'd get 5.5 steps which would fall outside of the scale.

Doing the maths, notes that fall outside of the scale would be (in steps):

4, 4.5, 5.5, 6.5, 7, 8, 10

Which if you normalize those notes to be in a single octave you will have every note in the octave.
cptnal
Jay F. wrote:
I sometimes saw 0V being referenced as a C or an A. But I'm no expert.


Nope - 0V means that signal will not change whatever note the oscillator is tuned to. 1V will change it to an octave up, and so on.

Or to put it another way, pitch CV is relative to the oscillator's pitch, not absolute as in C0, C1, etc.
Dcramer
“Another day older and deeper in debt!” This is fun!
Jay F.
cptnal wrote:

Or to put it another way, pitch CV is relative to the oscillator's pitch, not absolute as in C0, C1, etc.


Thanks for the clarification. That's what I understood.
I reckon I saw voltage associated to MIDI notes on MIDI to CV converters then.
Dave Peck
If you add the sequences together first, and then put that CV signal through one quantizer, it will stay in the blues scale (or whatever scale the quantizer is set to).

If you quantize each sequence separately and then add them, the result will no longer be in the original scale provided by the quantizers since it is being modified after quantizing.
cornutt
If both sequences were in equal tempered scale, then the output would also be in equal tempered scale, although the actual melody might sound very different. This is because in equal tempermant, a half step = 1/12 volt, so if you add two such voltages, the sum is still some multiple of 1/12 volt. In non equal tempered scales, not all notes are at 1/12 volt intervals, so once you start adding them, you are likely to get some notes that are "out of tune". (Keeping in mind that when you start playing with non equal tempered scales, what constitutes "in tune" is subject to interpretation.) For example, if you add a blues fifth to a perfect fifth, you get a blues second. eek!
Homepage Englisch
cptnal wrote:
Jay F. wrote:
I sometimes saw 0V being referenced as a C or an A. But I'm no expert.


Nope - 0V means that signal will not change whatever note the oscillator is tuned to. 1V will change it to an octave up, and so on.

Or to put it another way, pitch CV is relative to the oscillator's pitch, not absolute as in C0, C1, etc.


True, but when I play my midi keyboard through Doepfer Midi-to-CV, it will track down to a certain point on keyboard, and everything below that key (C,E,D; I forgot) will not change pitch, presumably some low (but not lowest) MIDI note giving 0V. VCO pitches are of course relative, but I try to tune them to correspond to a keyboard (when I'm using it - which is less and less these days).
oneunkind
C1+C2=C3(IN)
D#1+A#1=C#3(OFF)
F1+G1=C3(IN)
F#1+F#1=C3(IN)
G1+F1=C3(IN)
A#1+D#1=C#3(OFF)
C2+C1=C3(IN)
Navs
Is this new scale called the heavy or bad blues, then? cool
mskala
If you're going to add two sequences as control voltages and you want the result to be musically meaningful, it's usually best that at least one of the sequences move slowly and have only a few possible values. For example, if you have a melody sequence on whatever scale, and you have a second slower-moving sequence that is just the values corresponding to 0, 5, and 7 semitones, maybe with some octave shifts as well, then when you add them together you get your melody shifting between the tonic, dominant, and subdominant keys. Throw in the occasional 6 (half a volt) for jazzy tritone substitutions. You might drive the slow sequence from a clock divider if you want the shifts to happen on a consistent schedule.
cornutt
Homepage Englisch wrote:

True, but when I play my midi keyboard through Doepfer Midi-to-CV, it will track down to a certain point on keyboard, and everything below that key (C,E,D; I forgot) will not change pitch, presumably some low (but not lowest) MIDI note giving 0V. VCO pitches are of course relative, but I try to tune them to correspond to a keyboard (when I'm using it - which is less and less these days).


This is probably a setup function in your MIDI/CV converter. The MIDI note numbers have a range of 10-1/2 octaves, and it is rare to find a MIDI keyboard that can go all the way down to note #0. Your typical 49-key keyboard is configured so that the middle C key outputs note #60. That means that the lowest key on the keyboard (assuming that it is also a C) is note #36. However, on some, middle C outputs note #48, which means that the lowest C is note #24.

Typically a MIDI/CV converter will be set up so that note #36 produces either 0 volts are 1 volt. However, most converters have an octave shift function that can change this one or more octaves higher or lower. There are several reasons why; you might have connected a set of bass pedals (which usually will output lower note numbers), or you might want latitude to use octave select controls on your VCO. What it sounds like is that your Doepfer MIDI/CV has an octave select shift setting that needs to be adjusted.
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