·      If a song, or section of a song, ends with an FΔ7 chord, the preceding chord will usually be C7.  This combination of chords will be familiar to those with knowledge of formal music theory as a perfect cadence.

 ·      C is a fifth higher than F, so we can generalise this pattern by referring to it as        |  V7  |  I  |

 ·      Just as there is a strong tendency for C7 to resolve onto F, a G chord will nicely introduce the C7 (G is a fifth above C).  If you check the harmonised scale of F major, you’ll see that the chord on G is the minor 7.

 ·      Thus we have the sequence               |  G-7  |  C7  |  FΔ7  |

     or, in its generalised format             |  II-7  |  V7  |  IΔ7  |

 ·      This pattern  II  V  I  is one of the cornerstones of jazz harmony.  Mastering its possibilities is one of the keys to successful improvisation.

 ·      A useful rule is that wherever you encounter a straight dominant 7 chord, you can slip in a II-7 as well.  This is particularly common at the end of a chorus when preparing to go back to the start of the sequence again.

 ·      For example, take the simple sequence introduced previously:

 |  FΔ7  |  FΔ7  |  C7  |  C7  |  C7  |  C7  |  FΔ7  |  FΔ7  |

 ·      The run of four bars on the same C7 chord is boring and restrictive when it comes to improvisation.  A simple way of adding interest is to substitute alternating G-7 chords:

 |  FΔ7  |  FΔ7  |  G-7  |  C7  |  G-7  |  C7  |  FΔ7  |  FΔ7  |

 ·      Another tedious feature is the two FΔ7 chords at the end of the progression which, in an improvisation of several choruses, will be followed by two more bars of the same chord at the start of the sequence.  Here we can introduce a turnaround bar.  We substitute half a bar of G-7 and half of C7 for the FΔ7 in bar 8, thus:

 |  FΔ7  |  FΔ7  |  G-7  |  C7  |  G-7  |  C7  |  FΔ7  |  G-7:C7  |

 ·      The  II:V  turnaround bar is a very common feature of jazz songs.

 ·      As previously discussed, chords that appear in the same harmonised scale can be improvised on using notes of that scale, but with one or two qualifications, mostly to do with the problem of the note a fourth above the root of V7 and IΔ7.

 ·      Minor 7^th chords are not sensitive to weakness in the fourth, so you can play C against G-7 without too much trouble.  The notes that particularly differentiate G-7 and C7 are F and E respectively.

 ·      So a practical rule (but once again it’s only practical, not universal and unbreakable) is use the F major scale to improvise on all three chords,    G-7, C7 and FΔ7, but avoid emphasising the E on G-7, the F on C7 and the Bb on F.

 ·      You can get used to this idea by including alongside your scale and arpeggio practices exercises in which you play the notes of the F major scale from G to G¹ skipping over E (this will be the basic material for improvising on G-7), the notes from C to C¹ avoiding F (your C7 improvisation scale) and from F to F¹ omitting Bb (the FΔ7 scale).

 ·      Work out the  II-7  V7  IΔ7  chords for other major keys, and their “improvising scales”.

 ·      Now here’s something to think about.  If the II chord naturally precedes the V chord because it’s a fifth above it, and the V chord resolves onto I for the same reason, why shouldn’t we continue the process further?  And the answer is - why not?

 ·      So take a look at the note a fifth above II.  It’s VI.  In the case of the F major harmonised scale, that’s D-7.  If you can, try out the progression

 |  D-7  |  G-7  |  C7  |  FΔ7  |

 ·      Nice, isn’t it?  And it should be familiar too, because the  VI  II  V  I  pattern is another very common one in jazz.

 ·      And why stop there?  There’s a fifth above VI, and a fifth above that and so on.  You may have come across the term cycle of fifths.  This is what it refers to.  II  V  I  is just part of this whole business of the cycle of fifths, and the more familiar you are with the harmonic relationships within the cycle, the easier improvisation will become.

 ·      Experiment with the cycle of fifths within the harmonised scale of F major. How many fifths you need to build onto the front of  II  V  I  before you get back to  I  again?  See if you can work out “improvising scales” against the different chords, emphasising and avoiding particular notes from the F major scale.  Your ear will be your best guide to what works and doesn’t work with each chord.