It is possible for two people to communicate with out talking, seeing or listening.
do = left-hand pinky-finger/little finger
re = left-hand ring-finger
me = left-hand middle finger
fa = left-hand index finger
so = right-hand index finger
la = right-hand middle-finger
ti = right-hand ring-finger
Have both people sit at a table opposite of each other.
Have one person with their palms up, the other with their palms down.
Have one person cross their arms/hands.
Now both left-hand pinky-fingers, left-hand ring-fingers, etc are touching each other.
Now start talking so-re-so.
The right-hand pinky-finger could be used as a space or word spelling error signal.
This is also the format for using the number keys on a standard keyboard, if each finger was assinged to only one key. :)