Also you cant do this sort of thing in a hostile environment. It needs to be held with open and friendly people, otherwise its potentially going to be too distracting to pickup on nuances. already being held in a new space would likely be hard to acclimate oneself to it.
The music has to be very well known to the listener in order for it to be irrelevant. or there would have to be sounds or signals that would be neutral enough.
-The above comes from having gone to someone elses highly tuned system in an entirely new environment and trying to compare a dac. To a couple people familiar with that system, differences were immediately obvious that were difficult for me to pick up on. I think part of it was that I felt there was a bit of an expectaion for me to hear these distinctions, which was a distraction from the mental process required. After that experience I had occassion to compare a new cd player to a dac in my home and I had to go back and forth several times with a very small short piece of materials to try and tease out the nuances. But I was able to do it. Of course this kind of evaluation may be easier for other folks to do than myself. I do think there is some practice needed to learn how to retain a mental state to "listen for" things. This test may not really be as productive as it is hoped by some.
The speaker is the most critical component and I could imaine that the differences could be a lot more noticible than my experience in trying to differentiate one high quality digital source component from another, though.
