Modulation from major key to relative minor - what could be the pivot chord?

Question

I want to modulate from D major to B minor. I have a perfect cadence (A7 - D) in D major, after which I need to use a pivot chord to go into B minor. I was thinking of using the F# chord, but I am not sure if it should be an F#m or F#.

According to my knowledge, a pivot chord has to be common between the original key & the key you want to modulate into. If I have to use the F# chord, I would have to use A# as an accidental in the chord (since F# as a chord doesn't exist in D major). So should I use this chord, or simply write it as F#m? This means that the relative minor would have to be B natural minor. Is this ok?

Also, what other chords could be better ways of modulating into the relative minor? When modulations go into the minor, is it generally the harmonic minor which is used, or it depends according to accidentals (if any) are used?

Answer 1

a pivot chord has to be common between the original key & the key you want to modulate into...

Right. When dealing with relative major/minor keys like D major and B minor the key signatures are the same therefore all the basic diatonic chords are the same between the two keys.

From that perspective all the diatonic chords are potential pivot chords.

All you really need is the sequence of chords: pivot > new dominant > new tonic.

is it generally the harmonic minor which is used?

That isn't the only way, but it will do what is needed. (The natural minor won't work.) Without going into detail about how to handle minor key harmony, you must make sure the new dominant uses the raised ^7 degree of the minor scale. In this case it means using A# in B minor. So the dominant is F# major, spelled F# A# C#.

Beside that fact that any diatonic chord is potential a potential pivot, the simplest way to choose the pivot is to use a chord that will be a good pre-dominant to the new F# major dominant. Obvious choices by conventional harmony are iio6 or iv. Those chords respectively are C# diminished in first inversion E G C# or E minor E G B.

Just of illustration, I will take the first choice. In Roman numerals it would be...

D:viio6/Bm:iio6 V i

The slash indicates the pivot chord and modulation.

Answer 2

The main point of a V chord is the leading note. That's the main reason the harmonic minor scale notes get used often. There is no key of 'B natural minor', there is a scale, but in a minor key, the first 5 notes in any minor scale are identical, after which the notes from the parallel major or natural minor are game to be used.

F♯ chord doesn't exist in D. So what? We're not going to be in D any more, so it makes no difference.

By simple use of ears, try both, and hear that F♯ major (or dom7) is far more decisive than F♯ minir (or m7). If you're looking for a 'rule' don't bother. Have a listen to how V works in the majority of minor pieces - the fact that yours has modulated from the relative major is somewhat unimportant.

Answer 3

You can use the G major chord which is both D:IV and b:VI then you can move three steps back towards the e minor chord whis is both D:ii and b:iv and then have a Major chord built on f# with the leading tone of b minor resolving properly to make the modulation to b minor complete.

Answer 4

The relative minor root (Bm) IS a common chord (vi) of the starting key (D). Just play the cadence in D and continue with a cadence in b.

What about the false cadence? This would be the most usual modulation (followed by a perfect cadence in the relative key)

I-IV-V-I in D than I-IV-(V)-vi = i (Bm) = (D-G-A-D -> D-G-F#-b)

confirming Bm - Em - F#7 - Bm