in between major and minor

This is the first post of many I plan to make about Things I Like in Music.

If you've played around with Songsmith (and if you haven't, you should), you'll notice that instead of a switch between major and minor, we provide a "happy" slider that lets you explore a continuum between strictly major and strictly minor chord progressions. Is this really how music works, you might ask? Can a song be somewhere in between major and minor? Now, certainly a song can be major and minor in different sections, like the chorus and verse (Happy Together is a good example of this). Minor-verse-major-chorus (and its much rarer opposite) is also a Thing I Like in Music, but right now I'm interested in songs that sound both major and minor within a single section.

It turns out that many great songs do this, and wavering between major and minor is part of what makes them great. Here are a few examples (Roman numeral chord names assume the major key):

One Headlight
Listen to the verse, and notice how the first half of each line sounds just a little bit less gloomy than the second half, which helps give the song its poignant feel. The chord progression during the verse is VI -> I -> III -> vi, two chords generally associated with the major key followed by a minor cadence.

Just What I Needed
The same thing happens in the verses here. The first half of each line sounds happier than the second. Even the lyrics seem to follow suit. "I don't mind you coming here." Moderately happy! "And wasting all my time." Umm, not quite so happy. The chord progression in the verse is I -> V -> vi -> III, the two chords most indicative of a major key followed by the two chords most indicative of a minor key.

Say It Ain't So
The previous two songs (or at least their verses, which we were focusing on) probably sounded closer to minor than major. This song, to me, sounds closer to major. The chord progression is vi -> III -> VI -> I, this time ending each phrase with a major sound. Perhaps ends of phrases have a stronger influence on the overall feel.

Yesterday
Both sections of this song live in the mysterious land between major and minor, and it's generally considered one of the best songs ever (citation needed). Coincidence?