Vashon backing

In the Vashon Celtic Tunes chart for Out on the Ocean, the Part B starts out with the Em chord:

Out On The Ocean
Jig in G

Part A
G G | G D | G G | C D
G G | G D | G G | D G

Part B
Em Em | Em Em | D D | D D
G  G  | C  G  | G G | D G
Em Em | Em Em | D D | D D
G  G  | C  G  | G G | D G

Perhaps obvious?

Perhaps the choice of vi: E minor: (E - G - B) is a no brainer, given the melody lands right on the E note at both the 1 and 4 down beats (jig in 6/8).

X: 1
R: jig
M: 6/8
L: 1/8
Q: 1/4=100
K: Gmaj
%%barnumbers 1
|"Em""_1"e2e "_4"edB| "Em""_1"ege "_4"edB|

Other options

But just for analysis, let’s try out some of the options.

I: G Major: (G - B - D)

Not horrible, though the major colours it more bright.

X: 1
R: jig
M: 6/8
L: 1/8
Q: 1/4=100
K: Gmaj
%%barnumbers 1
|"G""_1"e2e "_4"edB| "G""_1"ege "_4"edB|

IV: C Major: (C - E - G)

I imagine the same for C.

X: 1
R: jig
M: 6/8
L: 1/8
Q: 1/4=100
K: Gmaj
%%barnumbers 1
|"C""_1"e2e "_4"edB| "C""_1"ege "_4"edB|

ii: A minor: (A - C - E)

If not major, then what about another minor?

X: 1
R: jig
M: 6/8
L: 1/8
Q: 1/4=100
K: Gmaj
%%barnumbers 1
|"Am""_1"e2e "_4"edB| "Am""_1"ege "_4"edB|

Doesn’t quite work either. So I think the Em is the very natural choice, having had a closer look at the melody.