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So II-V7 patterns occur when a minor seventh and a dominant seventh are a fourth apart or when a minor seventh moves to a dominant seventh with root motion that moves down by half step. This all being in Ionian of course. So does the same apply to the different modes?

Let's take C Phrygian fot example, would DbMaj7 to G°7 (or Gm7 (b5)) work as a II-V7 pattern? The II in this mode is not minor and the V is diminished but it also functions as a member of the dominant family. And they're also a fourth apart in the scale. Would you use modal interchange to change the chord types to bII-7 and V7? Or would Dbm7 to G°7 work because the Diminished chord has the same function as a dominant chord? Any clarity would help, thank you

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All of the normal modes are derived from the Major scale, where the tonic is a different degree from that scale. Your example concerns C Phrygian. Phrygian has the tonic derived from the third scale degree of Major, and C natural can only be the third degree of Ab Major, also known as Ab Ionian.

Think of the Ionian scale as its scale degrees: 1-2-3/4-5-6-7/1, or Ab-Bb-C/Db-Eb-F-G/Ab

Phyrgian has 3 as the tonic, so the scale would be shifted: 3/4-5-6-7/1-2-3, or 1/2-3-4-5/6-7-1, or C/Db-Eb-F-G/Ab-Bb-C

Here I wrote the chords out so you can see the difference compared to major. As you can see both Db and F are common between the Dbmaj7 and Ghalfdim7, with the Ab moving down a half step to G, C down a whole step to Bb, and the bass Db moving up an augmented 4th to G. The A4 is very important in a dominant chord in major, since the interval is rather dissonant and the notes are only a half step away from the tonic chord, as can be seen on the major side between F and B. B is pulled up to the tonic while F is pulled down to the third of the tonic chord. This interval is also only present between 4 and 7, which in Phrygian is now 2 and 5.

Next the bass moves up a perfect 4th to the tonic, C, making a nice cadence, while the soprano moves down a half step taking advantage of that flatted second degree half step which wants to resolve to the tonic. F moves down a whole step to Eb instead of a half step, so it's not quite as nice, and Bb and G stay the same.

When writing in modes it's best to take advantage of it's unique properties compared to its relative Major or Minor scale. Half steps tend to want to resolve the most and sound great doing so compared to whole steps. There are also many ways to voice the chords and lead the voices depending on what intervals you wish to focus on. In my example, if you added a Db to the V chord an octave lower than the soprano the augmented 4th between G and Db adds extra tension. Db is the unique tone in Phyrgian, and both the II and v chords have it, making them great chords to works with.

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    Thank you, that was an incredible answer and gave me a great understanding of using modes. By any chance have you encountered any pages or charts on the modal chord families? I can't find any and it would save me a lot of time for the other modes. – MusicMan Sep 29 '17 at 23:13
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    @MusicMan I don't have any charts with this because I don't think it's entirely necessary. Since modes are all derived from the Major scale if you learn the relationships between all the chords of the Major scale it will all transfer over. Any chord progression works not only on the chord's quality but also the intervals between them and the rhythm which accents certain chords or pitches above others. So I'm not sure what such a chart would entail. – Tama Sep 30 '17 at 0:05
  • I guess to specify, the dominant chords in Ionian are the V and Vii. In Phrygian or Aeolian, the dominant chords or the chords with the most resolution to the tonic would change. Obviously the V and Vii of Ionian wouldn't be the dominant chords of the other modes. – MusicMan Sep 30 '17 at 0:42
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    Tonic, dominant, and sub-dominant are functional based on their intervals, which I pointed out in my answer. Tritones tend to want to resolve back into stable perfect 5ths. Half steps and minor thirds tend to want to resolve to major thirds, a more stable interval. In minor keys the point is to be unresolved. Basic rules like these are why functional harmony work. You just have to apply these to the intervals present in any given mode. – Tama Sep 30 '17 at 1:38
  • Thank you very much, I appreciate it. I've always been confused on the matter. I'm a bassist and just got into chord theory etc – MusicMan Sep 30 '17 at 3:05
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For analytical purposes, the same roman numeral analysis can be used for modal music; however the function of the chords is not necessarily the same (depending on the mode). In phrygian, for example, the V chord is built on the fifth scale degree, but it does not function as a dominant chord. It has a different quality and does not have the same pull (or resolution) to the tonic. Generally speaking, even in modal music (at least in western, tonal music) chord progressions tend to have a "function." Tonic, dominant, sub-dominant are the three basic "categories" of chord function. Use your ears to determine what sounds unresolved and what has the strongest tendencies to move to the tonic chord. Again, using phrygian as an example, composers tend to choose either the II chord or VII chord as "dominant" to resolve to tonic. (So in C Phrygian, either Db major or Bbm).

  • Why exactly are the II and VII chords of Phrygian dominant sounding? Is there a more detailed page of details on this information? – MusicMan Sep 27 '17 at 3:15
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    I don't agree that the Phrygian bII or bvii have dominant functions. I generally hear bvii-i to sound more like a deceptive cadence and bII-i to sound more like the minor key's bVI-V. – Dekkadeci Sep 27 '17 at 14:10
  • I can't find a single book or page on the internet on this topic. It would be really helpful for future musicians or composers if we all could figure out a chart for the modes and their chord families. – MusicMan Sep 27 '17 at 17:29
  • Phrygian tends to not be used as much as, say, mixolydian. I know Respighi utilized it in Trittico Botticelliano. It often gets "modified," similar to the way we modify aeolian-natural minor to accommodate functional harmony. A I-II-III-II-I motif (progression) is often heard in TV or film scores to accompany bull fights or conquistador scenes. Em F G F Em which sometime becomes major phrygian. E F G F E. The bii of the mode is like a tritone sub for a dominant chord. – M-Squared Sep 28 '17 at 14:52
  • M-Squared, that's incredibly interesting. I appreciate the insight, is it the cadential motion of the notes within the chord then that'll tell you if a modal chord has a certain function? I love to stray away from Ionian but can't find much anywhere on modal chord families – MusicMan Sep 28 '17 at 20:45

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