You should already be familiar with the tonic, dominant and subdominant chords/triads. If not, please see Triads and Chords before reading this lesson!
The chord built up from the 2nd degree of the scale, or supertonic note, is called the supertonic triad, or chord ii.
The supertonic triad is made up of the 2nd, 4th and 6th notes of the major or minor scale. We usually use the notes from the harmonic minor scale to build the supertonic chord.
The supertonic triad in C major contains the notes D, F and A.
The supertonic triad in a major key is a minor triad, because the interval between the lowest note and the middle note is a minor third. Between the lowest and highest notes, the interval is a perfect 5th.
The supertonic triad in A minor contains the notes B, D and F.
The supertonic triad in a minor key is a diminished triad. The interval between the lowest note and the middle note is also a minor third, but the interval between the lowest note and the top note is a diminished 5th. Diminished chords are sometimes written with a small circle °, in lower case letters.
Chord ii is a ”secondary” chord. Most often, chord ii is followed by either chord V, or chord I in second inversion.
Here’s an example of a minor chord ii in a piano piece by Scharwenka. The key is G major, so chord ii is a chord of A minor. It is used in first inversion, with C as the lowest note. (More about inversions later in this chapter). In this piece, the chord is written as a broken chord (separate notes). The chord that follows it is Ic, the tonic chord in second inversion. Ic often follows iib because the bass notes move up by step, for example from C to D here, which sounds nice.
Here’s an example of a diminished chord ii°, in Mozart’s Piano Sonata in A minor, K310. This time the key is A minor, so the supertonic triad is a chord of B diminished. As before, chord ii° moves to a second inversion tonic chord of A minor.