Jam Night Last Night
Two words best describe it: Train Wreck.
First, they got off on bad footing by starting 25 minutes late.
There were 3 drummers there. One of them tied for best drummers there........WITH ME! And, I'm not a drummer.
Nobody could sing a lick. The "hosts" did a Billy Squier song (way over their head); who does Billy Squier at a jam night?
Guitar & bass playing was between pedestrian & rotten.
I played 3 songs, all directed by me. Took me 5 minutes for them to get the changes to All Along The Watchtower, which is just Em/D/F/D, every 2nd beat.
I took an amp & guitar, otherwise I would have left sooner. I needed the stage to clear to start packing up. It's all that kept me there.
Those guys seemed to be having fun, but I wasn't.
= new reply since forum marked as read
Long as I'm just playing rhythm guitar.
After that point, that would take real practice
His use of effects is outstanding.
Reminds me of the fusion bass players of the 70s.
We used to host jam nights here in town. Sunday afternoons, twice a month. (Every other. Another band hosted the "other"
We attracted a broad mix of talent, but it became better & better. The lesser skilled guys cane on the days we weren't the host, because the "competition" was stiff.
The club had its own sound system, and drums in the basement. So, we only brought amps. (Our spare stuff, because our regular gear was in the truck.)
We did this AFTER we quit playing regularly because my work travel schedule made it too fatiguing for me.
Some very good moments playing with others.
The opposite of last night.
Our other rule was for ourselves. We played no more that 4 songs to let the soundman dial things in. Then, we start calling people up. If it was a whole band, 3 songs & off. If they want to stay & come up again later, fine.
Our rule about people coming up to play with us was variable, depending on the quality of play. A hack isn't getting more than 2 songs.
My only objection to your post, (light-heartedly) is the major over minor thing. As a very modal player do that all the time. But, I'm playing the correct major scale!
I do that too but these 2 guys were playing a major chord on one side of the stage and a minor chord on the other at the same time. My ears folded in on themselves. 
When I was hosting we did basically the same as you. We played about 20 minutes to warm up the crowd and get things going and then the official Jam started. I got to know who were the less experienced players and the more experienced. I tried as much as was possible to mix one less experienced player with more experienced players. That gave the noob a chance to play with more solid players who were able to carry the noob through. It also gave the noob player a good feeling in that they got a chance to play with more seasoned players. It also sounded better to the audience out front rather than 4 or 5 noobs crashing through the audio equivalent of a dark room of cans and bottles.