You all are right. But it's missing how the old word ceili moved to
the new meaning.
Ceili was the old meeting in the neigbourhood (kitchen).
There was no fixed form, storytelling, music, dance, chatting and
whatever you do when you meet and you never knew about TV. At those
times you had the old dances taught by the dancing masters and you
danced them at night.
The church was always suspicious about music and dance as
entertainment. There are several stories about parish priests who
punished musicians and dancers. So in the early 1930s the church
realised if they can't stop the devil they must control him. They
started the dance hall act. Private dance was forbidden. All the
evil entertainment had to take place in the community hall, where the
priests were able to control it.
OK one fiddle was not loud enough. So we had to add a bit of volume:
Coleman was succesfull in the States with piano. Why not add piano?
All the drunken people make such a noise on the floor, that we loose
the rythm. Get us a drum and we'll sort them out.
This was the start for various "in fashion" instruments to be added
to a "ceili band". It seems to depend on the place you are in and the
crowd who makes the music to define "these instruments belong to **a**
I have seen ceili bands in Eire with fiddle, electric guitar, drum computer
and trumpet (only shortly! I run away in time :-)). The last band I saw
was a button accordion, silver flute, guitar and fiddle.
So to me (and thats a pitty I think) it seems, that once you call
yourself "Ceili band" you are allowed to do everything. With the
"Tulla Ceili Band" are other known bands you know what to expect. But
if you see "With ceili band" you better check before what to expect.
Back to the dance:
In former days you danced at a ceili, what you learned during the day
(from the dancingmasters). It was no active decision not to dance
set dances. In our days there is some sort of revival for the set dances.
And the people do exactly what they did at a ceili 100 years ago:
They dance what they know. There is no active decision by the dancers
wich says "This is a set dance. It belongs to a ceili night or not".
I always try not to find an academic rule what a certain word in folklore is.
I try to find out about the circumstances behind the word.
What would you tell somebody in twenty years if he/she askes you
"What does the word ceili mean and what is a ceili band?"