Tri-tone substitutions - when to apply and what notes to solo over?

RelayDuzzy

I'm just learning about tri-tone substitutions, and from what I gather, you'd use it in place of the IV7 or V7 chord.  The result to me just looks like the root but chromatic half step down or up.

Can you only substitute the IV and V chords within a key, or can you do it for any chord? 
What about soloing over a substituted chord, can you use the original chord's notes .e.g. if it's the V7 chord being substituted of G, can you use the D7 notes over G#7 chord?

viz

I don't really like the IV7 substitution, I don't find it very effective.

For the V7, it's good to explore the substitution in the context of a 251 because of the descending bassline, which is one of the things that makes it so effective: So, using Roman Numerals, in a ii-V7-I, you’re going to do a ii-bII7-I. 

And on that bII7 the best and easiest way to think of what notes to play is - either you play the notes of the substituted chord, or you play what you would have been playing over the V7 anyway. So in C major, instead of Dm-G7-C, the chords are Dm-Db7-C, and the notes to solo with over the Db7 are:

1) stick to the substituted chord's chord tones - Db, F, Ab, Cb (or B ). That's very basic, rather arpeggiated, but you can't go wrong.

2) Or if you play very simple stuff, you probably get away with playing C major throughout the 251 anyway, and you can do that over the substituted version too - it's not very interesting or musical but it works, just.

 3) Or over the Db7, you can sprinkle some G7 stuff as though you hadn’t substituted but that rather defeats the point, plus there’s a few notes you must avoid, like the D, because you’ve just moved off the Dm chord. Also I don't like the sound of the B or C there. The G, A, E, F are ok, plus you need to add the Db. 

4) Or over the Db7 you play G(alt) notes, which are G, Ab, Bb, Cb (or B ), Db, Eb, F, G. 

5) or it’s quite nice to do whole-tone scale on the Db, ie Db, Eb, F, G, A, B, Db. 

6) Or you can do octatonic / symetrical diminished. There are 3 versions of this; the best one is half-whole from G - so G, Ab, Bb, Cb (or B ), Db, D, E, F, G, but again I always think the D sounds odd. 

7) There's quite a neat trick Greg Howe showed me in a 251 in C; over the D, you play A minor pentatonic, to bring out the 2 of the Dm (the E); over the G7 (or Db7 substitute), you slip up a semitone and play Bb minor pentatonic, which has Bb, Db, Eb, F, Ab, Bb, which is perfectly in G(alt), as you can see from my 4th point above; then over the C you can slip up another semitone and play B minor pentatonic, which gives a lydian flavour to the C, as well as accentuating its major 7th (the B ). You just have to be careful to play purely pentatonic scales, no blue notes, just the pure pentatonic notes. 

RelayDuzzy

Thanks a lot Viz for the in depth examples!  That's quite a lot of options there.  I'm not familiar with the scales in 4,5,6 but will have to try each of them out.  But point 7 is a great tip and easy to remember - just moving upwards chromatically.

viz

Exactly! Plus I have a really good altered lick of Greg’s to play over the G (or Db) - I might youtube it. 

jpfamps

That pentatonic trick is well used by jazzers and very useful.

Regardless the tritone sub is a way of introducing some altered tonality over a 7th chord, so generally you would not be looking to play the notes of the V chord over a subbed tritone, ie you would not play D7 over a Ab7 resolving to G.

However, playing Ab7 over a D7 resolving to G will work, and is widely used to spice up your lead lines.

Why this works is that the key chord tones of the V 7the chord, the 3rd and the 7th, are also in the tritone sub.

The 3rd and 7th of the V7 chords are a semitone away from chord tones in the I chord, and are crucial for the resolution of the V to the I.

Try this: play the root and 5th of D (D and A) resolving to a G major chord. Now compare playing the root and 7th of D7 (F# and C) resolving to G major. The latter is a much more obvious and sastisfying resolution, due to semitone movement to the G).

If we are in G, the  ii V I is Am7, D7, G.

The tritone sub of D7 is Ab7, which will give Am7, Ab7, G.

The 3rd and 7th of D7 are F#/Gb (yes I know these are different) and C, and in Ab7 the 3rd and 7th are C and Gb/F#.

So the key semitone resolutions are preserved in the tritone sub.

The additonal chords tones in the tritone sub are Ab and Eb, which are also a semitone from the tonic G, so essentialy by employng the tritone sub you have added some extra resolving semitone movements. (By the way you can think of  those  Ab7 chord tones as the b9 (Eb) and b5 (Ab) of the V, D7).

Anyhow, this is why the tritone sub works very well when you are resolving around the cycle of 5th (eg V chord to I chord), eg in a ii V I, and not so well on a IV7 chord (as you mention this chord I assume you are playing blues!!) if you don't resolve it.

In a 12 bar jazz blues, this resolution would occur in bar 4, (I7 to IV) resolution, in bar 10 (V7 to I resolution), and where you are are using the VI7 chord to II chord.

A key feature of jazz blues is that the V7 to VI change in bars 9 and 10 is avoided like the plague, as this is not a very satisfactory resolution, whereas the V7 to I is. If you listen to a lot of 40 and 50s rocking blues (I do!!), especially anything piano based then bars 9 and 10 are often 2 bars of the V7 or a ii/II7 V7 change.

You also find a lot of early country music avoids the V7 to VI change too.

Re note choices chord tones will work fine, and, as Viz says, are a good staring point. Other chord tones from the Ab7 that work and I like are the 13th/6th (#9 of D) and the 6th (aug 5th of D), so 9th and 13th arpegios work well too.

If you want to use  a scale based approach, then you would use the lydian dominant scale of the tritone sub, ie Ab lydian dominant. This is a major scale with a raised 4th and a flattened 7th, and is a mode of the melodic minor. The diatonic arpeggios from this scale work well.

Another cool trick using a tritone sub is in a VI7 II7 V7 I7 chord progression in swing and blues is to play this as alternate #9, 13th chords, which in G would be E#9, A13, D#9, G13. If you tritone sub the IV and the V7, you end up with chromatically descending 13th chords, so in G that would be Bb13, A13, Ab13 and G13.

Asleep At the Wheel use this type of chromatic movement in the turn around in their version of Route 66 (they also use a #9 on the V in the intro too!).

https://www.youtube.com/watch?v=vifUaZQL8pc

RelayDuzzy

Thanks for the extra in-depth explanation and advice!  Will definitely try these out!