But then how do we analyze the B major chord in measure 3? It contains a D#, which should be a clue that something strange is going on.

The first chord is G major, which poses no problem – that’s I. A simple example of a borrowed iv chord occurs in the intro to Radiohead’s “No Surprises.” The iv is probably the borrowed chord used most frequently in major keys, and it sounds especially good when followed by I. Used in a major key, the minor iv chord can be an especially effective tool to tweak the listener’s expectations. In E major, for example, we would look to E minor, which would give us the following chords. To find borrowed chords we might use in a major key, we will pretend like we’re in the parallel minor key, then think through what the iio, III, iv, VI and viio7 would be in that key.

Note that we label them “bIII” and “bVI” rather than just “III” or “VI” because their roots are altered - in C major, the third scale degree is E, but the third scale degree of C minor is Eb, so borrowed chord based around the third degree has a root of Eb. We will not worry much here about that distinction. Theorists also sometimes call bIII and bVI chromatic mediants, depending on their context. For example, if we’re in C major, we can “borrow” chords from C minor. That was easy, right? Now, the reason that matters here is that, especially when we’re in a major key, we can use borrowed chords from the parallel key. So the parallel major of C minor is C major, and the parallel minor of E major is E minor. Two keys are parallel when they share the same tonic. Two related concepts are parallel major and parallel minor. C major is the relative major of A minor because both keys have no sharps and no flats, for example. In Chapter 1, we discussed the concepts of relative major and relative minor, which referred to major and minor keys that shared exactly the same notes. Borrowed chords in minor keys are less common, but we can sometimes borrow the I and IV chords from the parallel major. When we’re in a major key, we can “borrow” chords such as iio, bIII, iv, bVI and viio7 from the parallel minor key, which means the minor key of the same name.

Chord progressions b flat major