A user asked on the forums how one can introduce probabilities into the ER-101/102 sequencing and thus this video was made to explain one method. The video is a quick tutorial on how to have individual steps trigger (or not) according to a (per-step) probability.
You can do this with the non-destructive transforms of the ER-102 groups because these transforms get re-evaluated every time the step is played. The trick is to get the ER-101/102 to threshold the output of the random operators. In other words, to get different probabilities just use the fact that parameters are clamped to be at least greater than zero and then combine the subtract operation with either the jitter (jt) operation or the (rd) operation.
For example, suppose we have 8 steps that are all the same DURATION=16 but have the following TRIGGER lengths (i.e. GATE lengths but track is set to TRIGGER mode):
Then we add these steps to GROUP #1 and set the X/LOW transform of GROUP #1 to
A = -20 (i.e. subtract 20)
rd = 20 (i.e. add a random number between 0 and 20)
The steps with the larger TRIGGER lengths will have a higher probability of being greater than zero after the group transform is applied. This way you can set the effective probability of a non-zero TRIGGER length per-step. In the example above, steps 1, and 5 will always fire but steps 2 and 6 will never fire. The other steps will fire with probability proportional to their TRIGGER length with anything greater than 20 having 100% probability. It's quite fun and allows you to create ever changing rhythms that nevertheless have a clear groove, in fact any groove that you want. Finally, you can use the MOD bus to control the "probabilities" with external CV.