The Tri-tone Substitute

​     Modal Jam Theory is anything but conventional (actually - it's much more 'stream-lined' than what is described in this article) - but for a better understanding of how the 'Circle Of 'C' can be divided by the 'G' and the 'Db' -- we must explore what can be found in most conventional textbooks: The Tri-tone Substitute.
     The short story of everything to follow in this article is that the 'Db7' produces the same critical 'active' tones ('Fa' and 'Ti' in the key of 'C') as the 'G7.' Both of these chords may set the ear's strong anticipation to resolve to 'C.'
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          The Tri-tone Substitute

​     If you have studied at the university level – you are familiar with the Tri-Tone Substitute (Db7) for the Dominant Chord (G7) in the key of ‘C.’ The following is a brief explanation of the mechanism(s) involved in the Tri-Tone Substitute:
     The critical “active half-step” tones of a G7 are ‘B’ and ‘F’ (‘Ti’ and ‘Fa’ of the Home Key Center). When we look at these same tones in the Db7 (the Dominant Chord with its root at the Tri-Tone), we find that this chord also contains the same tones – but their roles are reversed.
     In the G7 – ‘Ti’ is functioning as the Major 3rd of the chord – and ‘Fa’ is functioning as the b7 of the chord. In the cadence of G7 - C (V - I) – ‘Fa’ resolves to ‘Mi’ and ‘Ti’ resolves to ‘Do.’
     In the Db7 – ‘Fa’ is functioning as the Major 3rd of the chord – and ‘Ti’ is functioning as the b7 of the chord. In the cadence of Db7 - C (bII - I) – ‘Fa’ still resolves to ‘Mi’ and ‘Ti' still resolves to ‘Do.’
     As is the case with all concepts of chord substitution – I would not suggest that Db7 – C sounds the same as G7 – C --- it does not. When we analyze the Db7 – C cadence, we also hear the sound of ‘Ra’ resolving to ‘Do’ – and we hear ‘Le’ resolving to ‘So.’ This chromaticism is not inherent in the cadence of G7 – C.
     The sound of the Tri-Tone Substitute (Db7) resolving to the Tonic (C) is much more “colorful” than the sound of the Dominant (G7) resolving to the Tonic (C) – but the ear remembers ‘Fa’ and ‘Ti’ of the Home Key Center – and, as we know, the ear is always listening for a way home. 

The Color Of 'Fa'