Critical listening and altered states

Ok, this is not a question about relaxing, but about listening to evaluate how the system (or a piece of gear is sounding).

What, in your experience, are the pluses and minuses of altering your state of mind for listening? This can include anything you've used to affect your everyday state of mind, from coffee, beer, scotch, tobacco, to much stronger — and psychoactive, dissociative — additives.

What do you gain by altering your consciousness in terms of what you notice, attend to, linger on, etc?
What causes more details to emerge?
What allows you to stick with a thread or, alternately, make new connections?

Or perhaps you like to keep all those things *out* of your listening; if that's you, please say a bit about why.