I believe the example uses 6, but as mentioned the
generalized to an arbitrary number of tape drives. Personally I think
to do it Hollywood style, you'd need at least 6 drives and it would be
even more impressive if you could get something like 12 drives all in
a row grinding away on it.
To do it Hollywood style, you just need to make the tapes
move ... pause ... move ... pause ... (with nearby panel having
lots and lots of unlabeled lights flashing randomally)
Switches and knobs on the panel-of-lights are a plus.
You don't need to have it actually doing anything, just a
simple program to tick the drives every second or so (rewind
at end of tape and start over), and a rack of blinking Christmas
tree lights sitting nearby. You don't even need to sync the tape
drives to the lights, or worry that most of the lights blink