Originally Posted By: alan S.
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If the 7b9 appears as a VI chord in a I VI II V progression then it's being used as a secondary dominant of IIm7. Jazz is fundamentally a chromatic music and secondary dominants are one of the oldest chromatic devices in music.

Secondary dominants, usually chromatic types as you know are used all the time to lead into diatonic scale degree chords. So the major third leads into the bVII tone of IIm7 by a half step resolution and the root of IIm7 by the same half step in the opposite direction.

They can have the effect of turning the chord they resolve into a temporary tonic; a kind of transient modulation.
You can choose to relate to that temporary tonic or treat the whole 1 6 2 5 sequence as a passage in the key to which the 5 chord resolves.

Jazz works this way melodically as well, with chromatic embellishments or enclosures leading up to or placed around a target chord tone. In each case its a matter of tension and resolution occurring at a high rate in the accompaniment and the improvised line.

HTH

Alan


Yes, Alan, understood, but this does not explain the presence of a flat 9, is this simply a chromatic passing tone? As a function of the IIm functioning as the one its a flat 6th, though this position (IIm) would indicate a dorian minor


Just musing...

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