Dargason or Sedany
for a line of men facing a line of a like number of women, for as many as will
Reconstructed by Dafydd Cyhoeddwr, with guidance from Master Trahaearn ap Ieuan's version (from KWDS4)
This dance is unique in its setup, so it has a unique repeat structure.  For the first two progressive figures, the formula for repeats is (nx5)-2.  
For the last figure, the hey, taking each change as 4 beats and with everyone changing at once (or  as many as can), the necessary added repeats equal the number of couples in the dance
With this formula - (((nx5)-2)x2)+n - 3 couples = 29 repeats, 4 = 40, 5 = 48
Music: There are many sources for perfectly acceptable music for this dance, but no commercial source has enough repeats even for the 3 couple version
iTunes building block playlists
Part 1
Figure 1, Repeat 1
1&2: Couple 1 alone side left
3&4: Couple 1 alone set and turn single, left  (Note: do not change places here)
Figure 1, Repeat 2
1&2: Couple 1 pass each other on the left to side right with couple 2
3&4: Couples 1 and 2 set and turn single, right
Figure 1, Repeat 3-n
1&2: Pass your old partner on the left to side left with the next person in line
3&4: Set and turn single, left
R: Dancers advance, alternating sides, until they reach the end of the line and have no new partner.  They turn around, wait out a repeat, and start with the next person to come to them.
Continue until everyone is back to their places.  When everyone is back where they started, the next part can begin, though live musicians might mean that the next figure can start early
Figure 2, Repeat 1
1&2: Couple 1 arm left with each other 
3&4: Set and turn single, left (Note: still no changing places)
Figure 2, Repeat 2
1&2: Couple 1 pass each other on the left to arm right with couple 2
3&4: Couples 1 and 2 set and turn single, right
Figure 2, Repeat 3-n
1&2: Pass your old partner on the left to arm left with the next person in line
3&4: Set and turn single, left
R: Dancers advance, alternating sides, until they reach the end of the line and have no new partner.  They turn around, wait out a repeat, and start with the next person to come to them.
Continue until everyone is back to their places.  When everyone is back where they started, the next part can begin, though live musicians might mean that the next figure can start early
Figure 3
1-n: Hey with hands until you get back to where you started.
This reconstruction requires 4 beats per change, *and* that everyone able starts the hey at the same time (for example, for 4 couples, man 1 and woman 1 switch, man 2 and man 3 switch, woman 2 and woman 3 switch, the 4s watch)
This results in getting back to place in the same number of repeats of the music as there are couples, making piecing the music together much easier