Hi Colin

Interesting question. I have similar questions looking at this from Australia. I have started running workshops titled something like "Modern New England Contra Dance". (This is not to alienate folk from other parts of the US, but most of my exposure to contra has been in New England). Then I can focus on what the elements of such a dance are, which is what makes the modern contra dance scene what it is. 

Then there is the historical stuff, ie what led up to contra's current distinctive style, without which the current dance style would not have evolved. And the innovation (eg techno contra - see comments below about music), without which it will stagnate. But I don't talk about this in a dance workshop - this is nerdy caller stuff.

Then there is the music. Is dancing to anything other than what I would call contra dance music strictly contra dancing? We have related forms of music in Australia which have evolved from the same roots, but have a different feel. I would argue that the pure New England Contra style needs to be accompanied by pure contra dance music. A reel played in Irish style can have a completely different feel to the same tune played in contra style. I can hear the difference but can't currently describe it in words  - something for somebody's PhD I suspect. I think the package of the right dance and the right music is incredibly important. And of course, there's the innovation ie techno contra.

I visit the US contra scene as often as possible, and can see and hear changes in the style between visits. So it is constantly evolving. Eg on  my first visit in 2003 a square was often included in what I would call "an evening of contra dance" as distinct from a "contra dance" (to get around the terminology of a contra dance referring to both a whole program and a single dance). On my last visit I don't recall a single square being included on a program. And the formations were almost exclusively duple improper and becket. 

As with anything in life, as soon as we try to classify something (especially something that is evolving), the list of exceptions is usually longer than the list of inclusions. Ask any taxonomist :-)

Long may the discussion and debate continue!

Cheers

Jeanette