Hello everybody !
Resumption of the discussion, with another solution because I had not properly posed the problem, nor what I wanted to obtain: a progressive and random variation in voltage with a period of more than 3 minutes, or even 15 minutes.
The easiest way to get this "random LFO" seems to be the use of 3 LFOs with fairly close frequencies and mix them. Each LFO delivers a bipolar sine wave, modulated by the random voltage coming from itself, made unipolar by the addition of a DC voltage of 5 V, and negative by its processing in the attenuverter. At each cycle, the frequency is thus modified. If the Random is -1 V it is divided by 2, and for -3 V divided by 8 (2 to the power of 3)
The DC Source 1 button also globally modulates the speed in the same ratios : with a starting frequency of 0.02 Hz, and -5 Volts applied, it becomes 0.000625 Hz, i.e. a wavelength of 1600 s (26mn 40s)
Button 2 is set to 5 volts and should not be changed. It says 10V because there are 2 cables... This makes the random voltages of each LFO positive, then inverted, so they just slow down the frequency. You can adjust the amount of these slowdowns by moving the fader button. This can further increase the division of F up to 2 to the power of 15 (10+5), or for 0.02 Hz initially, you obtain 0.00000061035156250 Hz or a wavelength of up to 18 days 23h 6mn 40s in theory !
Finally, the amplitudes of each LFO in the mixer are modulated by their own inverted ramdom, to reduce patch accelerations when the value is near 0.
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Sorry there were a mistake on the R_Ware Control learnings... it's corrected :
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the patch :
and a musical try with 3 patches (let it breathe)