It is generally accepted that the first printed version of “Greensleeves” dates from 1580 as a broadside ballad but that almost certainly means it existed for at least a little bit before this. (The publication history of this tune is pretty crowded; lots of versions, lots of different lyrics and lots of titles. I'm not even going to try to trace that since it can be found elsewhere.) But it is still not likely old enough to have been written by King Henry VIII in spite of the persistent rumor and unfortunate attributions on sheet music. He did write music and lyrics for existing music but he didn’t write this tune or any of its lyrics. Anonymous should get all the credit for this little song.
The color green had a number of associations in the Renaissance. Sleeves in this era could be detached and switched out for a colorful splash if you had the money for that sort of thing. Green skirts, on the other hand, was a slang reference to grass stains and likely not for any respectable reasons. But green was also used to represent fidelity and is still very much a color associated with the fairy-folk. All of this has been used to claim the green sleeves in the folksong lyrics mean the woman in question was an upper-class lady, a virtuous woman wrongly suspected of being a prostitute, an actual prostitute, a fairy or just a someone who liked the color green. Most likely, we won't ever know.
There are several versions of this melody in natural minor, melodic minor, Dorian mode and major. I’ve even run into someone claiming this tune was Eastern European in origin. This could explain why there are so many competing versions since when tunes travel that far, they are often changed and shoehorned into different musical systems. But there was no musical analysis offered to support this idea so that particular theory must be left in the entirely unproven category. Most people I know play this tune in A minor-ish but G minor-ish is fairly common and of course it can be transposed to any starting note you like. One more thing to remember is this song can be written in different meters. Some form of triple meter (6/8 or 3/4 frequently) is more common in my experience but plenty of people have shifted it into duple or even odder time signatures.
Now here is what I have noticed about this tune.
Musically, what sounds “right” to a society changes over time. During the European Renaissance, the musical sound was shifting away from modes (scales that sound odd to modern ears) and towards the major-minor system (what Western listeners are most used to today). “Greensleeves” uses both systems and therefore shows that transition as it was happening.
The earliest version was printed in minor and since major just sounds wrong to me, I won’t examine that version.
The minor version starts out in the older Aeolian mode but uses the more recent melodic minor scale for the cadences at the end of phrases.
Aeolian (same as natural minor) uses lowered 6th and 7th scale steps. This scale is used throughout the tune when there isn’t a cadence approaching. The chorus actually starts on the lowered 7th scale step, a distinctly modal sound.
The ascending melodic minor scale raises both the 6th and 7th scale steps. This scale is used exclusively at the end of phrases.
Now, the Dorian version still follows this basic pattern - the tune starts in the older Dorian mode and switches to the more recent melodic minor for the ends of phrases.
This sound clip demonstrates the Dorian mode, melodic minor and a short run through of a Dorian version of this song. (You may notice that this version starts one whole note lower than the Aeolian version. This can create the impression that this version is darker or sadder when played right after the other one. It is an illusion created purely by the contrasting starting notes.)
Dorian is almost the same as Aeolian (natural minor) but has a raised 6th.
Melodic minor is actually closer to Dorian than Aeolian in some ways.
(For a more complete explanation of the different modes see my earlier post Modern Modes.)
Perhaps one reason this 400 year old melody remains so popular is that it gives us a small sweet taste of the different variations in music when the collective musical ear was shifting between different scale patterns, creating variegated melodies and harmonies that shimmer and shift with each hearing.