Adding a fourth chord in a 2-5-1 chord progression

Question

Background

I understand this might be a rather vague question - and I apologize if it is too much so - but I am novice music theorist and think this question does have merit to it.

I am playing a 2-5-1 7th chord progression in the key of E major on my guitar in the following voicing:

   F#m7  B7  Emaj7
E|--9-----7----7--
B|--10----7----9--
G|--9-----8----8--
D|--11----7----9--
A|--9-----9----7--
E|--------7-------

Which sounds great, obviously, as 2-5-1 are well-established chord progressions.

What I am trying to accomplish

However, when I play through it a second time, to switch things up, I conceptualize either a different second chord or an added chord in-between the second and third chord of the progression, like so:

   F#m7   ?  Emaj7
E|--9-----?----7--
B|--10----?----9--
G|--9-----?----8--
D|--11----?----9--
A|--9-----?----7--
E|--------?-------

or

   F#m7  B7   ?  Emaj7
E|--9-----7---?---7--
B|--10----7---?---9--
G|--9-----8---?---8--
D|--11----7---?---9--
A|--9-----9---?---7--
E|--------7---?------

Where the new chord in either example would be in a higher pitch/octave that resolves to the 1 strongly. I feel like I have heard stuff like this before and can conceptualize the sound I want to make, but can't quite find the voicing on the fretboard.

What I have tried

I have tried B7 higher up the neck along with Amaj7, C#min7, D#dim, and D#m7b5 along with playing triads of each on the first three strings to no avail. I can't quite shake this chord I'm thinking of. I can hum it, but still no luck finding it, so I decided to come ask here.

Question

So ultimately my question is, is it common to add to or alter a 2-5-1 chord progression? If so, which chord(s) work well both in general and specific to my example? Apologies in advance if I misspoke on anything - again, I am a novice theorist trying to learn from others in the community.

Answer 1

Yes, you can modify it. In fact, one of the principle ideas of music is repetition with variation, so your intuitive desire to modify the progression makes sense to me.

Categorical approach with new chords placed in parenthesis...

• extend the roots by descending fifth harmonic sequence backward

(vim7) iim7 V7 Imaj7

• insert passing chords

iim7 (viio7/V) V7 Imaj7

• swap out (or insert) similar harmonic function

(IVmaj7) V7 Imaj7 ii and IV are both subdominant function

iim7 (IVmaj7) V7 Imaj7

iim7 V7 (viio7) Imaj7 V and viio are both dominant function

• deceptive progression

iim7 V7 (vim7) | iim7 V7 Imaj7

• tritone substitution

iim7 (♭II7) Imaj7

iim7 (♭IIalt7) Imaj7

• borrowed chord, modal/chord quality alteration

iim7 V7 Imaj7 | iim7 (iim7♭5) V7 Imaj7

iim7 V7 Imaj7 (imin6) | iim7 V7 Imaj7

• secondary dominant alteration

(II7) V7 Imaj7

(VI7) (II7) V7 Imaj7

(VI7) iim7 V7 Imaj7

• modify chord extensions

iim7 (V9sus4) (I6)

• modify chord voicing

I think the number one thing to keep in mind is: if the modifications don't alter the original functional progression, things should "work." In terms of function...

• passing chord don't have function, that's why they are called "passing", you can place them between any two otherwise functionally progressing chord
• changing chord extensions and voicings doesn't change the chord function, it's really become a matter of voice leading/linear movement
• borrowed chord have the same function as the original diatonic chord, ex. IV or borrowed vi both function as subdominants and can go where functional subdominants go
• any chord can be preceded by its dominant, might be best to keep this to chord with a major or minor triad base so that the secondary dominant's dominant role is convincing, not that of these four bullet points only this one involves true functional difference

Another way to think of these things is this. The original progression is just diatonic descending fifths. So, what are the various standard categories of chromatic chord? Those are: secondary dominant and borrowed chords. Depending on details and how you classify, those categories overlap with chromatic passing chords. You just need to know where those chromatic chords go. If you refer back to the maintain the original function idea, that should provide a reliable guide.

You may notice I've used the term - functional - a lot, and I've made no mention of - "you can do whatever you want", or "not all harmony needs to be functional" - and while those two points are true, the progression ii V I is the epitome of functional progression, so I decided to build my answer around the tried and true methods of functional harmony.

When I try these ideas at the keyboard I find you often can't haphazardly throw a bunch of things together. Sometimes you have to play around a bit until you find the internal logic and feel that "works." And subtle changes are sometimes all you need to make things fall into place. So don't just trash ideas that don't work immediately.

If guitar chord voicing/fingering becomes a challenge when trying to learn about this harmonic method, consider working things out at a keyboard, and then transferring the music back to guitar. Just a suggestion. Personally, I have a lot of trouble visualizing harmony on the fretboard compared with the keyboard.

Answer 2

There are really many choices, and the choices can be functional or artistic or both. With an artistic choice, it doesn’t have to have any specific function, it just has to sound good to you.

In both instances the most obvious functional choice which maintains the feeling of the resolution is for the ? chord to be an F7 (X-8-10-8-10-8). F7 is a substitute dominant, a 7th chord that is a b5 or tritone away from the regular V chord, B7. Since they share the same dissonance between the 3rd and b7th they function in a very similar way.

Another approach is to just play another B7 but of a different quality, like B7+ or B7b9.

There are many other choices available, say an Fmaj7 (X-8-10-9-10-8). This sounds great and also functions as a chromatic passing bII chord going to the I.

A more colorful less functional approach might be a D7 (X-5-7-5-7-5). This is a chord borrowed from E minor, the parallel minor, as is the Am suggested by @Divizna in comments. Really there is no limit as to what you can come up with.

In answer to your final question, yes it is pretty common to alter or add to a ii-V-I or any chord progression for that matter. Usually the style of music will dictate how and how often it is done.