THE­ORY GOD­MOTHER

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Guitar Techniques - - TALK BACK -

David Mead sorts out your mu­si­cal malaises and cre­ative co­nun­drums.

Ac­cept No Sub­sti­tute Dear The­ory God­mother

Please could you ex­plain to me how tri­tone sub­sti­tu­tion works?

Derek Tri­tone sub­sti­tu­tion, or b5 sub­sti­tu­tion as it is also known, is one of the more con­fus­ing ar­eas of mu­sic the­ory. When I was plough­ing my way through the­ory books many years ago I read the ba­sic rule that went some­thing like: “You can sub­sti­tute any chord which has the flat 5th of the orig­i­nal chord as its root”. All well and good, but it’s not strictly ac­cu­rate or very clearly ex­plained; fur­ther­more, they don’t say why it works. So let’s look at why tri­tone sub­sti­tu­tion can be used in jazz and other re­lated mu­sic styles.

The chord that lives at the heart of tri­tone sub­sti­tu­tion is the dom­i­nant 7th. The dom­i­nant 7th de­mands some sort of res­o­lu­tion, the most com­mon of which is the V-I. The rea­son why this works is that ev­ery dom­i­nant chord has a dis­so­nant b5 in­ter­val be­tween its 3rd and 7th (Ex 1) and when this is fol­lowed by the I ma­jor, that dis­so­nance is re­solved. What hap­pens in a V-I res­o­lu­tion in C ma­jor is that the G7th’s 3rd and 7th both shift by a semi­tone to form the C’s ma­jor 3rd, the most con­so­nant in­ter­val in mu­sic (Ex 2). So what you’re hear­ing is the move­ment be­tween a dis­so­nant (tense) in­ter­val to a very con­so­nant (set­tled) one, hence the sen­sa­tion that things have re­solved and the mu­sic is now at rest.

Tri­tone sub­sti­tu­tion ex­ploits the fact that a b5th can be looked at in two ways. In our ex­am­ple, the notes B and F moved a semi­tone each in op­po­site di­rec­tions to form C and E, but what hap­pens when we look at it up­side down? That gives us F and B which just hap­pen to form a b5th in­ter­val too. No other in­ter­val in mu­sic will do this, so if we look at the dom­i­nant chord that con­tains F as its 3rd and B (here re­ferred to a ‘Cb’ be­cause of the key sig­na­ture) as its 7th, we find Db7 – a dom­i­nant chord ex­actly a b5th away from G. Db7 will re­solve nicely into Gb ma­jor (Ex 3) but, be­cause of the b5th or tri­tone in com­mon be­tween G7 and Db7, it will also ‘stand in’ for G7 and make a plau­si­ble sub­sti­tute for it. Try com­par­ing both in Ex 4 and you should hear that the res­o­lu­tion is sound in both cases.

To sum up, if you find a V-I res­o­lu­tion in a tune, it’s of­ten true that you can sub­sti­tute the V chord for a dom­i­nant a b5th away. There are more uses, too, but I think it’s best that you fully un­der­stand the ba­sic con­cept be­fore you move on to its more ad­vanced ap­pli­ca­tions.

Scal­ing The Blues Dear The­ory God­mother

Could you tell me why the six-note mi­nor Blues scale is con­sid­ered to be mi­nor Pen­ta­tonic with an ad­di­tional note (b5th), and not a di­a­tonic seven­note scale with one note sub­tracted?

Jakob I think the rea­son is be­cause that’s how many gui­tarists come to the Blues scale in the first place, Jakob - they learn the mi­nor Pen­ta­tonic and then find this ex­tra ‘cool’ note to tack on. But you can’t view the Blues scale as a di­a­tonic scale be­cause the truth is there are no regular scales that con­tain three semi­tones in a row, as the Blues scale does (4-b5-5). If you took one note away from any di­a­tonic scale you wouldn’t end up with the Blues scale at all.

The­o­ret­i­cally, the mi­nor Pen­ta­tonic is the Nat­u­ral mi­nor scale with two notes miss­ing (2nd and 6th), and the mi­nor Blues scale sim­ply adds the b5th as a pass­ing note. But in prac­ti­cal terms for most gui­tarists it re­ally is the mi­nor Pen­ta­tonic with the b5th added.

(There’s also the ma­jor Blues scale, which is ma­jor Pen­ta­tonic with b3rd added, but we won’t go into that here, although Ex 6 shows Ma­jor and Mi­nor scales be­side their rel­a­tive Pen­ta­tonic).

Get­ting back to mi­nor Blues scale, if you fac­tor in the blues ‘curl’ - the b3rd pushed slightly sharp or slightly ‘ma­jor’ - you get a scale that looks rel­a­tively sim­ple on pa­per but which can cover a mul­ti­tude of mu­si­cal sit­u­a­tions.

Many gui­tarists then add the full Ma­jor 3rd, and then the 6th and the 9th to cre­ate hy­brid scales that are great for pretty so­phis­ti­cated im­pro­vi­sa­tions. And, as if by magic, turn to page 16 and Jon Bishop will ex­plain this very con­cept in glo­ri­ous Technicolor!

Lo­co­mo­tive Breath Dear The­ory God­mother

I love play­ing Ev­ery Breath You Take by the Po­lice ( Gui­tar Tech­niques Dec 2014), not just for the great tune but also as an ex­er­cise in strict tim­ing, arpeg­gio tech­nique and palm mut­ing. But no mat­ter how much I work on my fret­ting hand I can­not do the stretches from static chord po­si­tions. So I end up rac­ing up and down the neck fin­ger­ing ev­ery note separately. Is there some other so­lu­tion?

Colin The span of the hand does im­prove with prac­tice, Colin, and this tune is a good work­out in or­der to bring it about. The only tip I can pass on here is one that Andy Sum­mers him­self told me, which is that he uses his first fret­ting hand’s fin­ger to play both the bass note and the ma­jor 3rd in the tricky Aadd9 chord (and like­wise for the b3rd in the F#m9) which ac­tu­ally makes it a lot eas­ier to play and cuts down the stretch some­what (Ex 6).

The only other thing I can ad­vise you to try is to capo the neck around the 4th or 5th fret and prac­tise the tune in a dif­fer­ent key (with smaller fret stretches) un­til you nail the fin­ger­ing, then drop the capo back a fret at a time un­til you’re play­ing it in the cor­rect key. As I say, the span of your hand should in­crease over time and you should soon be per­fect­ing your per­for­mance of the song - take it one breath at a time!

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