Jim,
Brood frame as found in the majority of my hives are as you suggest - not completely fixed
onto the bottom bar.
But as for leaving a continuous lax of wax - they tend to be fixed in the central areas
and "unfixed" near the lateral area.
I have thought that this was due to the need for passage of bees from comb to comb.
Also, the period in which the comb was placed into the brood area appeared to have
influence on how the comb was drawn out.
When the brrod area was in a period of full expansion and with a reasonable nectar flow -
then the wax seemed to be well attached.
Other times when the lower parts of the frame were under less pressure to be put into
service - chewing and removal of wax occured.

 How would a bee facilitate it's analysis of what the "dancing bee" is trying to
> communicate on a variable sound board?

I'm not sure what you mean by "variable sound board".  The sound board
can be assumed to be non-variable, at least for the duration of any one
dance.

By this, I was refering to the fact that due to the presence of materials being in
different physical states, the propagation of vibration throught the area being vibrated
would change (speed and intensity).
Would a bee pick up the same "message" from the area of comb filled with liquid honey
compared to the same message generated on an empty area?
Would any difference result in a different response in the "receiving bee"?

You state from your experience that dances tend to occur on areas devoid if honey - maybe
there is a reason for this. -so much to investigate and so little cash!!!

Deveating from the topic in hand , would it not be worth the biscuit for established
centres to research to create a network of investigators. These delving into areas that
accredited centres are unable to due to lack of time, resources and cash. Subjects that
may by themselves be relatively unimportant when taken in isolation - but when linked to
other gathered knowledge might give the edge on the acceptance or rejection of a theory?

Anyway,
Refering to bees trained on odour containing sugar solutions - pages 309/310 of "Bees"
authored by I.Khalifman state that "as far back as 1939, foremost beekeepers reported at
the All Union Agricultural exhibiton in Moscow that with the help of trained bees  .......
2 to 3 fold increase in precious clover seed."
This text continues that so called trained bees were used on various other plant crops.
If this is true, then the idea that there is no transfer from artificial feeder to field
supplies is not so. I have no evidence myself supporting or rejecting this.

The above mentioned book makes interesting reading - if only for the manner in which it is
written!

Peter