Roger,

This is possibly not going to be at all helpful, but...you can identify the tonic note in minor keys in the same way that, even though there were those couple of lead in notes, you identified that the Rose Tree tune "started" and ended on G. I get the "sense" of what the start and finish notes are because of a sense of resolution of the melody.

If the melody feels unfinished then you probably aren't listening to the "end" note. Some of those really earwormy tv jingles often play on that sense of unfinished melody to make you want to start replaying the tune in your head again. A little like the written music I have for The Munster Cloak, in G major. To achieve that sense of resolution you have to bring the melody back to G to end it - otherwise it would never end, but just keep going round & round in your head.

The minor tunes do seem to evoke a more subdued or melancholy feeling than the major tunes.

By the way, I forgot to put line breaks in my neat little treatise on thirds and fifths.

Should have looked like this:

"So:
C D E F G A B
1 2 3 4 5 6 7

1st is C, 3rd is E, 5th is G.

If, for example the key is G major, with one sharp on F, then:

G A B C D E F#
1 2 3 4 5 6 7

If it was in a minor key like A minor (i.e. the tonic note is A, but there are no sharps and flats) then:

A B C D E F G
1 2 3 4 5 6 7