Relative Elektron newbie here, I’ve been absolutely loving my time with the Syntakt for the last month. One day I might even post something I’ve recorded on here 
I’ve searched the forums here and couldn’t find an answer to this question, so I figured I’d ask and see if anyone has any ideas.
What I’m trying to achieve is a sequence using song mode where a given track or group of tracks set to the chord machine play a “random” chord based on obviously predefined chord trigs and conditional locks.
Ideally, I’d have song mode set up to loop 4 or more patterns, and each time a pattern plays, a single chord plays which chokes or prevents any other chord trigs from playing. This is for an ambient performance and the idea would be having a probability of one of several different chords playing on each bar, but only ever 1 chord per bar (which would keep me from having to limit my list of chords and notes due to consonance with each other). I could manage this in a simple way by setting up individual tones, say, in a pentatonic scale, but having done things like that in the past, it isn’t particularly musical for my own taste. I’d rather set up pre-defined chords that sound good and contribute to my performance on other instruments.
I’m bad at explaining things sometimes, but just to try and condense that: I’d like something set up to loop in song-mode that allows me to have 1 random chord playing per bar, from a pre-selected pool of possible chords (more than 2 options per bar).
However, when I spent some time today working out how to manage this with _pre and _nei, etc, I couldn’t for the life of me figure out how to set a song up to do this. The best I could manage was figuring out the logic to select between one of two chords per bar based on % probability and _pre. You’ll have to forgive me, because it’s been over 10 years since I took a discrete math course 
but I can’t help the feeling that there’s some workaround to let me achieve this effect.
Apologies if I’ve not explained well enough or I’m in the wrong place!