Example of environmental interference:
At my old apt, my [ISTP] roommate was playing Bob Marley quietly on his laptop nearby, as I dozed on the couch.
I had some dream of working in a huge movie theater/arena.. all the employees wore headsets to communicate. At some point Bob Marley's Redemption Song started to come through my earphones.
My coworkers seemed to enjoy it, they hummed as we passed one another. I began to hum, as well.
Woke myself up, doing so, just as the song was ending.
Lex: [awake] ..how long was I doing that..?
ISTP: last half of the song.
Lex: [scratches head] ...was I.. on-key, at least ?