# How is modulation to the dominant achieved?

In any key, there are two adjacent keys to work with; The subdominant and the dominant. Let's assume that we are in a major key. Modulation to the subdominant is easy. The leading tone is a vital part of the key, and flattening it to turn a tonic into a dominant 7th in the new key is extremely effective to modulate to the subdominant. It works immediately.

Modulation to the dominant is much harder. To sharpen the subdominant(which is not a tone in either chord I or V) is nowhere near as effective as changing the leading tone. Even if we use a V(7) in the desired key as a pivot chord, it still sounds like a V(7)-V rather than the primary dominant. I have tried the common idea to cadence in the new key, but even after a couple echo cadences, the dominant function of the supposed new tonic still dominates(no pun intended). It almost seems easier to move through every possible subdominant, eventually reaching our desired key. I'm aware of breakaway and pivot chords, but they always sound like secondary dominants.

How is dominant modulation achieved?

Can be done in many ways, quite a simple way to do it:

This uses a deceptive cadence to get to VI to prepare the secondary dominant II7 to get to V, which still has the character of a half cadence. Thus we add a cadence on the dominant to enforce the dominant. Note we do not go I-IV-V-I on the dominant but I-I6-IV-V-I, as a I-IV on the dominant would have a tonal implication of V-I on the tonic. In this particular case I am using a secondary dominant in the new key because A) I was short a note and B) it strongly enforces the new tonic. Instead of going into a full cadence one could end this on a half cadence and continue in the new key.

Try using an even more distinctive, 3-or-more-chord cadence in the dominant's key. V - I of V may not cut it because it sounds too similar to V/V - V, but these sound harder to mistake for mere secondary dominant use in the home key (assume all of the following are "of V"):

I6/4 - V - I

V7/V - V7 - I

vii°7 - V7 - I

I6/4 - V - I of V may be the most effective of these because V6/4 (e.g. G/D in C major) is very rarely used, if at all.

A few ways.

The simple flattening of note ^7 of the prevalent key to get to IV. As in C>C7>F.

Used in many pop songs, the flat 7 chord itself. A sort of plagal cadence. As in C>B♭>F.

TTS - tritone substitution. There the 3rd and 7th notes in that same chord are interchanged, to become the 7th and 3rd of a new chord. As in C>F♯7>F.

Use of Vm (or Vm7). As in C>Gm>F.

Use of Go7. As in C>Gm7♭5>F.

Going the other way, the time-honoured is V/V, the secondary dominant, which in this case is a genuine one, C>D7>G.

Or, again using a diminished chord, a favourite for pivoting with, C>Co>G.

Or, a sort of extension of that, C>D7♭9>G.

And finally, C>A♭7>G, another tts.

Hope that's enough options to be going on with!