I watched a Terence McKenna lecture once, and he said the crushed peganum harmala seeds + mushrooms produces what he called Vegetable Television.
I can't remember the lecture's title, so I can't give a reference to it online, but he said Vegetable Television was seeing a streaming variety of patterns, without being overwhelmed by it.
When I did acid for the first time, when I was about 16, I would see stuff morphing into other stuff, and I was completely overwhelmed cause I couldn't make it stop.
So if harmala lets me see that again, but this time with interest in it, then I'm down for that.
I also can't remember if he said to smoke the seeds 30 minutes prior to mushroom ingestion, or 30 minutes after mushroom ingestion.
So, not much help here, other than McKenna vouching for it, which I'm down for that.
I also believe I've heard there can be difficult, or even detrimental effects to the combination.
If you find out any other info, I'd like to hear about it. I need some more research/confirmation before I try it as well.