I notice in the earlier thread that it is stated that Irish tunes tend to be Dorian, Scottish Mixolydian. Apologies.

It is also noted that, in the Dorian, because of the way the T-S structure works in Dorian, the dominant chord in any Dorian key (let us use D for the moment) is usually the VII, and not the standard key Vth -- which in this case would be a C major, which I guess explains the hovering back and forth between the tonic (D) and its right next door neighbour (C) which someone said was characteristic of the Dorian.

[Is this why Guest, whatever wants to call D the "relative dorian" of C major?] yours, Peter T. P.S. Thanks also to Art for the dulcetry.