♭VII-I Cadence, ♭III-I Cadence: Name?

Question

I've gone through a bunch of ♭VII-I and ♭III-I cadences in rock music. In C major, they are B♭-C and E♭-C.

Is there a specific name for the two cadences? So far, I've been calling them authentic cadence variants, since both ♭VII and ♭III are substituting for V. Others had been saying so, as well.

Answer 1

No. A widely cited scholarly paper calls them just what you do, ♭VII-I and ♭III-I. It offers a plethora of adjectives to distinguish different kinds of cadences, but none have the centuries of weight of the terms for the cadences that Mozart used.

Edit: One might call them variants of the authentic cadence, but that's an awfully broad name, not the specific name that you ask for.

Answer 2

I think you should distinguish between cadences and simple chord progression.

Cadences demark phrase or section endings.

A chord change that does not end a phrase or section is a simple progression.

In tonal harmony there are standard cadences: authentic, half, deceptive, and plagal. Some of the terminology gets applied to chord progressions in a more generic sense with no connection to phrase/section structure. Usage like cadential harmony or deceptive progression are examples.

In modal harmony, both folk music and Medieval/Renaissance music there are cadences other than those in tonal style. Now and then I've seen some names applied to modal cadences, but nothing like the standard naming in tonal style.

You could call ♭VII-I a modal progression or cadence. I have seen that used as an actual structural ending in folk songs and it such as case cadence would be a appropriate description.

I've not seen ♭III-I used as a true cadence, at least not commonly, but that kind of thing is a fairly common progression. You can describe the change as a chromatic mediant. It has a very distinctive sound.

Of course you can end a phrase with any kind of chord change. The question only becomes whether or not it's common enough to have a name. If it doesn't have a common name, it doesn't mean you can't use it as an ending.

The textbook Kostka, Harmony contains a classification chart for cadences...

Cadence type    First chord                     Second chord

Authentic       Contains leading tone           Tonic
Plagal          Does not contain leading tone   Tonic

Deceptive       Contains leading tone           Not tonic
Half            Does not contain leading tone   Not tonic

...it doesn't seem to be widely used, but it's logical. Also, it's followed by this statment...

A still more general but useful method of classifying cadences puts them into two groups: conclusive (authentic and plagal) and progressive (deceptive and half).

By that classification:

• ♭VII-I is conclusive, plagal
• ♭III-I is conclusive, plagal

...the critical point being there isn't a proper leading tone in those progressions.

Answer 3

The bVII7 I cadence is called the Backdoor Cadence.

See also a discussion on this "delicate Backdoor cadence".