modulation

[Derek]

I think I finally understand how gradual, common practice era modulation works. Basically, you proceed through a progression of chords that are common to the start and destination keys, and then when you reach the chord of modulation (perhaps the dominant of the new key), you might want to do some kind of cadence to help establish the new key (maybe hit the tonic of the new key briefly, then move back into a cadence as though to say: yes, we've really arrived in the new key) Is that basically it? Or is there more to it? (aside from the obvious fact that there are hundreds of ways of doing this).

[keyofc]

I think that's a nice way of putting it.

[schartmanovich]

Your summary sounds fairly accurate to me; however, I think it can be put more simply.

For a gradual modulation:

1) use a chord that is common to both keys and move toward a non-cadential progression to I of the new key

2) confirm the key with a cadence (HC, IAC, or PAC)

To have an authentic cadence of any kind, the penultimate dominant must appear in root position and usually has a 7th attached, but not always (i.e. V7-I NOT V6/5-I or any other variant with an inversion). A complete cadential progression will also include a pre-dominant chord to precede the V7 (e.g. II6, Fr6, IV6, VI, and a host of others).

Here is an example of a simple modulation from I to V

Key of I: I - V4/2 - I6 - VII6 - I - [V4/3] of VI - VI
Key of V:                                                    II - "I6" - II6 - V4/2 - I6 (non-cadential) - [V6/5] of V - V7 - I