Analysed: random LFO in Reason

I decided to test the random LFO modes of Propellerhead Reason devices. Random LFO offers a great way to add analog irregularities to a signal, modulating a synth parameter randomly or applying it to an effect. Instead of a boring fixed sound it will create a more uneven and imperfect sound. In other words: very analog.

For this analog-like smoothness what we need is what Propellerhead calls a Soft Random LFO.

CV analytics tool used: CVA-7

I used the Pongasoft CVA-7 rack extension for analysing the bipolar LFO signal. This free rack extension is in my opinion a must have for CV users who’d like to measure the CV signal.

Test results

Soft Random LFO of Dr.OctoRex
Soft Random LFO of Subtractor
Soft Random LFO of NN-19
Soft Random LFO of Thor
Soft Random LFO of Europa


Although in above graphs the CV outputs of the Subtractor, NN-19 and Dr.OctoRex are looking a little different from each other (duh! you’re looking at randomised CV outputs), if you analyse them over a longer time they seem to be generating the same type of smooth randomness.

Conclusion 1: The Smooth Random LFO modes of Subtractor, NN-19 and Dr.OctoRex are the same.

You will notice that the CV output of Thor looks a little weak. In general the CV outputs of Thor are weak, lower in volume than most other devices. An irregularity of Thor. A flaw.

Conclusion 2: The Smooth Random LFO signal strength of Thor is a little weak. I won’t recommend using it for triggering other devices. Use a Subtractor, NN-19 or Dr.OctoRex instead.

Europa seems to be using a slightly different randomness algorithm (it’s the last LFO setting) compared to the Subtractor, NN-19 and Dr.OctoRex. In a short time span the Subtractor, NN-19 and Dr.OctoRex often will always show randomised maximum plus and minus values (close to -1 and +1) while Europa might show average values while going to extremes only now and then.

What about Grain? It seems to be using exactly the same LFO section as Europa.

Conclusion 3: Europa and Grain will generate the most random LFO.

I also tested the Malström and the Pulsar Dual LFO.

The Malström doesn’t even have a random LFO! Curve 7 might look random but its pattern gets repeated over time.

Pulsar Dual LFO has a Random mode but it’s not a Soft Random type so it will generate a square wave-like CV output. Adding Lag to the signal helps smoothing out the edges a bit but it never gets as smooth as a true Soft Random LFO.

Conclusion 4: The Pulsar Dual LFO and the Malström are not capable of generating Soft Random LFO.

The big conclusion: For Soft Random LFO use a Europa, Grain, Subtractor, a NN-19 or a Dr.OctoRex device. Europa and Grain will generate the most random LFO.

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