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ii V I ?

Discussion in 'General Instruction [BG]' started by Paul4703, Oct 20, 2009.


  1. Paul4703

    Paul4703

    Mar 19, 2007
    I've come across this but yet to understand it. Can anyone explain in simple terms how a ii V I defines a key centre?
     
  2. I'm sure the more technically minded people on this site will give you chapter and verse, but first ask a gui****/Keytard friend to play you Dm, G7, C - you'll hear why.
     
  3. onlyclave

    onlyclave

    Oct 28, 2005
    Seattle
    'I' is the tonic, the Home chord
    'V' is the dominant or the second strongest function chord with the tonality. Playing V-I is the strongest cadence in western music and it gives the ear finality.
    'ii' is a subdominant function chord, substituted for 'IV'. The root is a perfect fifth away from the V, so just like the root movement from V-I sounds strong, the root movement from ii-V sounds strong, but since the quality of the ii chord is minor there isn't that same harmonic finality.

    You read on this board "Learn the circle of fifths!" and ii-V-I is a great example of that. Dmi - G - C (ii-V-I), Bmi - E - A (ii-V-I), Fmi - Bb - Eb (ii-V-I). Just pick any position on the circle and move clockwise. ii-V-I.
     
  4. BillMason

    BillMason Supporting Member

    Mar 6, 2007
    Perfect answer - I'd only add that in the Roman numeral nomenclature, lower case letters (eg. ii) signify chords with a minor third, whereas upper case letters (I, V, etc.) signify chords with a major third.
     
  5. JTE

    JTE Supporting Member

    Mar 12, 2008
    Central Illinois, USA
    ii V I defines a key because of the notes in the chord. In the whole spirit of being more inclined to teach you to fish than to give you a fish, let's look at it this way. But in order to really LEARN this, dig into theory so you know exactly WHY it's these notes.

    A. The ii chord is built by stacking thirds starting on the second note of the scale, the V is built by stacking thirds starting on the fifth note of the scale, and the I is built by stacking thirds on the first note of the scale. Use the key of G for an example, and write out what you get when you stack thirds up to make four note chords for each of these three notes.


    Done with that yet?

















    OK, you should have written out that the ii chord is A C E G, the V is D F# A C, and the I is G B D F#. If you don't know why it's those notes do some work on how to build a major scale and what a third is....


    So, the notes in the ii chord are the A C E G, and the notes in the V chord are D F# A C. That covers all the notes in the key of G except for the B. And if you think things through you'll know there's no diatonic major scale that has a Bb and and F#, so B MUST be the note. That's just from the ii V progression. Toss in the I chord and you've got the B note in those chords too.

    Plus- LISTEN to a ii V I progression. That Amin7 to D7 just sounds right. Then follow that with the G and you hear the chords resolving to bring your ear home to the G.

    THAT'S why ii V I defines a key.

    John
     
  6. there are whole books devoted to ii V I and if you want to improvise over changes it would be prudent to dig into it ,in all keys......look up autumn leaves chords
     
  7. Ten Four One

    Ten Four One

    Dec 5, 2006
    What they said.

    The root is obviously the center, but how do you know it's the root? Basically once you've committed yourself to using those seven notes, you've sort of defined the tonal center of the key, but the question is HOW do you use those notes to really signal where the center is & that its not some esoteric mode or something.

    Music is about tension & release. So how do you get tension and how do you figure out how to release it?

    The V chord has a lot of notes that are dischordant to the I - a seven and a nine. Two notes adjacent to the I. The V7 goes one step further and introduces a "tritone" - the most dischordant interval in music, so much so that the church outlawed it (and Jimi Hendrix used it as the intro to Purple Haze).

    Put this all together and you get a chord that has a very strong desire to get rid of all those dischordant notes & settle somewhere - like the I. The I is the most stable and least tense of places you can be, plus with all those adjacent tones piled up & the way the tritone works, I is the place a V7 wants to go.

    IV is a very stable chord - a fourth, a pretty major sixth, and the root. But it is the other chord in music. There are only 3 chords. [see why here].

    So what do you do to spice life up a bit? Well a ii chord has a lot of the same notes as a IV chord which make it a good substitute, and it also happens to be "the five of the five" - a fifth above the fifth. It's also a bit more tense for a number of reasons - it's minor, it gets rid of the root and replace it with a 2 (which we saw before, is tense when compared to the root), and being the fifth of the fifth, it wants to go to the fifth the same way the fifth wants to go to the root (but not as intensely), so it leads naturally to where we want to go.

    And there you are ii, V, I and why it defines the tonal center of a key.
     
  8. bobknowsbass

    bobknowsbass

    Jul 27, 2009
    Monrovia, CA
    When you learn what a ii-V-I is all of the sudden jazz makes a lot more sense.
     
  9. nothumb

    nothumb

    Sep 20, 2006
    NYC
    the V-I resolution is "satisfying" or easily processed by the human ear for reasons both according to the laws of physics (read up on the overtone series and the way we perceive sound) as well as our cultural lexicon (most every genre of western music uses it prominently, so if you have listened to western music all your life you have been 'trained' to expect and recognize it).

    a very short explanation of he overtone series is this - any note you hear has a number of overtones, or basically shorter sound waves that get increasingly dissonant as they get smaller. the note at twice the frequency of the tonic is an octave - a very consonant tone. the third overtone (one third of the original wave) is the fifth - again, consonant. the overtones progress in this way - the next ones are the perfect fourth, major third, minor third and so on. if you think of this on a stringed instrument, it's very simple... fret the string in exactly the middle and you get an octave (12th fret on a bass). fret it a third of the way down and you get the 5th. a quarter of the way down gives you the perfect 4th. so the notes we perceive as the most consonant in music theory are closely connected with the actual length of the sound waves involved and the ratio of one to the other; the ear seems more able to make "sense" of certain simple ratios (1 to 1, 2 to 1, 3 to 1... as they get more complex the sound is more dissonant). in this sense all the notes of the major scale are present in the root note through its overtones, such that when we hear them played in other notes and chords, we have essentially already 'heard' them through the tonic and come to expect them. (this isn't a perfect way of phrasing it but you get the drift). this is why the circle of fifths works... in each case, the closest non-octave overtone is the fifth, so when you resolve from the fifth it sounds 'natural' or pleasing to the ear.

    as someone else mentioned, the major second and major seventh of any major scale are both part of the V chord (say, the D and the B, respectively, in the key of C, are part of the G major chord). when a melody resolves stepwise to the root, either in ascending or descending fashion, either way the nearest note is part of the V chord, so it's very common to hear a melody resolve from, say, D to C over the chords of G and C respectively.

    the ii chord, being the fifth of the fifth, resolves in a satisfactory manner into the V chord while also signaling to us that the V is not the tonal center, because if it was, the ii would be major. so it's a natural way to lead into the V without implying the V is the tonal center. (as an aside, very often you will see key changes preceded by a ii-V-I in the new key because it is a very palatable modulation between closely related keys; so for instance, if you were modulating from C major to G major, you might see the progression of A minor - D7 - G major. this provides a progression that is not too jarring to the ear - it starts on a chord that is common to the two keys and moves along the circle of fifths - while simultaneously giving a clear signal that the G is the new tonic.)
     
  10. Paul4703

    Paul4703

    Mar 19, 2007
    Thanks to everyone who replied. The info clarified things for me and I think I've now got a handle on it.
     
  11. EADG mx

    EADG mx

    Jul 4, 2005
    Remember that all of this doesn't mean much if you can't hear it.
     

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