Interesting point Kingme. Different levels of 'Psychedelia' (ie Shulgin scale, levels of immersion, dissociation) are key here. A full on dose might provide inspirational raw material, but your fingers don't behave quite as dexterously as usual. Wait until you calm down and sketch your ideas. Heavy doses don't work with gigs. I did one on strong LSD when I was 16 in 1990. Apparently I played OK, but it was a trial of willpower to stay on track. Everyone in the audience (of 40 people or so!) had animated red lighting across there eyes like KITT off of KnightRider! There was too much extraneous psychedelic noise for comfort.
Later, when RCs and there kindred became available, I dabbled in low to medium doses of 2CB which worked subtly. I usually don't jump about like a mad thing on stage, but with a whisper of 2CB and I let loose somewhat. My Mrs (unaware of my synaptic tomfoolery) commented that I looked more into it than usual. Not sure if it affected quality either way but if looking like you are enjoying yourself is important to your act there is mileage to be had.
The most fun I have had i performing with an empathogen on board. Whilst recommending caution, it seems that in a busy noisy venue or outdoors, stronger doses are more noticeable. I usually go 1.5 times my usual dosages for MDMA and relatives (5/6APB, M1 etc).
Intuitive judgements like 'that was a good show' are slightly unreliable, but subjectively it does seem the case. Musicianship is not harmed by sensible dosages. Assuming your material is decent (One usually hopes so. . .) and you're on the way. Loosening of emotional expression is a good thing up to a point. You have to work out your own sweetspot.
Does the stage and maybe amplification provide a medium for the 'Contact High'? I don't know either way.
The people who come to see you after the performance are perhaps not the best people to be objective, and I can't remember a gig where there hasn't been compliments paid. My wife is the only person I trust to be objective on such matters since she is not a music obsessive like myself and has different taste. As a musician, you are are witness to your own mistakes. Those kinds of statistics speak for themselves.
But above the level of technical mistakes, there's that reading between the lines stuff, expression, sensitivity, band cohesion and interplay, listening attentively to your buddies contributions as much (if not more) than your own. The fusion of all these feedback data and the generation of your own happens almost unconsciously on a good night. Whatever your Drug Of Choice, it needs to be at a dosage that does not mess too much with those processes, but just widens there freedom of operation slightly. I'm perhaps a bit uptight emotionally from time to time so for me, that kind of loosening of inhibition can be useful.
I do always find some location to smoke a small joint before going on stage, but I spend much of my waking hours stoned so it's effects beyond normal are negligable. . .
I'm going to strum my acoustic for a while before supper.
Pipp out.