How does knowing the tri- tone of a 2-5-1 progression, Ex. dmin7, G7 to Cmag7 help in improvising?

Answer 1

Not sure what you mean by "tri-tone" in your example. You've got a straight-ahead 2-5-1 progression there.

I've heard of tri-tone substitutions, which is using a substitution of the dominant chord (V chord) with a harmony whose root is a tri-tone away... example:

2-5-1
Dm7 G7 CMaj

tri-tone sub.
Dm7 Db7 CMaj7

But your question was how does this help you improvise? Well if you know all the ways in which you can establish a tonal center with a cadence or phrase ending, then the world is your oyster, so to speak.

In other words, if I can go along in F like this:

F Gm7 C7(b9) C#dim7 Dm9

I can go in any direction in my improvisation! I can stay in F by finishing the phrase with a simple 2-5-1 like this:

G9(+5) C11(b9) FMaj9

or I can recognize that I have already established Dm harmony and go in that direction. I've already got a 7-1 in the minor there, and so I can stay in the new key, or I can recognize that the Dm harmony is actually a 2 in the new key of C. So now all I need to do is go for a 2-5-1 in that key.

The 2-5-1 sequence is like a "hidden portal" to go from one key to any other key. These shifts allow your melodies freedom to move in any direction you wish.

Many famous songs (new and standards) use a 2-5-1 progression in various ways. Think about Satin Doll. It starts out with a 2, 5 and 2, 5 again, but goes up a step with the sequence, then it ends with the tri-tone sub I mentioned above. It makes a great little phrase.

If you had a dollar for every famous tune that is built on almost exclusively 2-5-1's then you could buy a 90-ft yacht. Seriously.

Answer 2

After working with triads and seventh chords it should be obvious that there are scales and chords within scales. Many players like to think of the D minor (dorian) scale as a C major scale beginning on the second scale degree of C.

c d e f g a b c d

Since each of these scales share the same key signature, this way of thinking is natural and useful. Another commonly used scale that is also found within these two scales (with a key signature of no sharps and no flats is the G7 (G dominant 7th scale).

As you can see, anytime a C major is played for and octave and a half or more you are also sound the D minor (dorian) scale and the G7 (dom. 7th - mixolydian) scale. All three have one thing in common: a key signature of no sharps and no flats. The fingerings are the same, too.

Relate the dorian minor scale to it's related major key which, of course, lies one whole-step down from the minor. C major = D minor (dorian) = G7 (dominant 7th or mixolydian). These 3 scales share the same key signature - no sharps and no flats - and have identical fingerings.