You can consider La Chapelloise as the French version of the Gay Gordons; you dance in a circle, sometimes forwards, sometimes reversing, watching out for your toes, changing partners. A really rather lively dance and a very good way to get to know everybody...
You need a partner, you'll dance with them the first time through and maybe get to see them again sometime later, and you join in what should become a large circle on the dancefloor. If you are dancing the 'man's role', you'll head to the inside of the circle and you are both facing anti-clockwise round the room. That fits, the 'man' has his 'lady' on the right hand side as is the normal way of doing things and everyone is looking at the back of the heads of the couple in front of them...
You are not changing direction you are moving even through you've turned round. You continue with four steps backwards and you've found your partner's hand again....
Now you can change direction and head back where you came...
Leave a little gap between you at the end of this movement - you are going to need that space to spring sideways into....
You are side-by-side, facing anti-clockwise, with a gap between you and there's just a little tension in your arms as you are going to...
You are a little way apart again, facing anti-clockwise, with the lady on the inside and the man on the outside...
You are moving into the other person's place except that you are dancing with a different person (it's a mixer⬀) the lady moving back one place round the circle, and the man looking for the 'next' lady.
You still facing anti-clockwise, man on the inside, new partner on the outside and you start again...
There's a flourish possible on the turn when heading back, the man lifts his arm when taking the ladies right hand and lets her turn clockwise underneath. This leaves you nicely in place for the spring together...
It's done to 16 bar jigs, all quite light, quick and snappy. The sort of thing that keeps you on your toes...
The French Wikipedia entry, Chapelloise, flags it as originally Scandi with the name Aleman's Marsj (Allemannsmarsj), becoming La Chapelle-des-Bois when arriving in France in the 1930's, and La Chapelloise in the 1970's
In contrast, the German Wikipedia (and the English entry has followed this), flags it as being brought from the US to Scandinavia (and being given the name All American Promenade, or APP), with it originially deriving from the Gay Gordons.
Occasionally appears as the Progressive Gay Gordons. The moves are the same but you'd dance the A part with left hands, hand in hand, in front of you and the man holding his right arm up as if to rest his hand on the woman's right shoulder but really she has her right hand there and he is holding that (described as a Varsouvienne hold)