Understanding Tritone Substitution in Music Theory

[00:00:01]- Hi, I'm Gareth Green, and in this video, I'm going to try and answer a question that many people have.

[00:00:10]What is a tritone substitution?

[00:00:14]And when would you use it, what's it all about?

[00:00:17]It sounds like something incredibly complicated.

[00:00:20]So, let me see if I can break it down in a way that makes sense.

[00:00:24]So, the first thing to say about a tritone substitution is that a tritone substitution is a non-diatonic chord.

[00:00:34]So, what do I mean by that?

[00:00:36]Well, a diatonic chord is a chord that comes inside a key.

[00:00:41]So, if I'm in the key of C major, I'm using the scale of C major, and I make chords on each note of that scale by adding a third and a fifth above the root note, the bottom note, I get this chord, it's chord I or a C major chord, chord II, or a D minor chord, chord III, or an E minor chord, chord IV, or an F major chord, chord V, or a G major chord, chord VI, or an A minor chord, chord VII, or a B diminished chord, and then I'm back to where I started.

[00:01:16]So, those are the diatonic chords in the key of C major.

[00:01:22]They use the notes of the key signature, which is no sharps, no flats.

[00:01:26]But sometimes you want to add a bit of colour, bit a flavour to a piece of music.

[00:01:31]And you might use a non-diatonic chord.

[00:01:34]In other words, a chord that uses notes that are not in the scale of C major, but the chord somehow works.

[00:01:43]It sometimes has a function in relation to the key of C major.

[00:01:48]So, that's the first confusion because people look at these sort of chords and they go, "Oh well, it's not using the notes of the scale of C major.

[00:01:54]"It must be in some other key."

[00:01:55]Well, yes and no.

[00:01:56]But the point is, it's a non-diatonic chord.

[00:02:00]It's not using the notes of the scale of C major.

[00:02:03]But the point is this, it has a function in the key of C major, which is what we'll go on and talk about in a moment.

[00:02:11]So, it works in C major, even though it's using notes that don't belong to C major.

[00:02:16]But because it's using notes that don't belong to C major, it's adding a bit of colour, bit a spice to the music, which is why it's such a useful chord to use.

[00:02:26]So, that's the first thing.

[00:02:28]It's a non-diatonic chord.

[00:02:30]Okay, let's think about this word tritone.

[00:02:33]I mean, what does tritone mean?

[00:02:36]Well, tri is three.

[00:02:38]So, tritone is three tones, all right?

[00:02:43]So, if C to C-sharp is a semitone, or what's sometimes called half step, well, C to D is a tone or a whole step.

[00:02:55]So, if I put three of these tones, or three of these whole steps together, what do I get?

[00:03:01]If I start on C, well, one whole step, or one tone, takes me to D.

[00:03:06]Another whole step or another tone takes me to E.

[00:03:09]And another whole tone, or a whole step, takes me to F-sharp.

[00:03:14]So, one, two, three tones.

[00:03:17]So, C to F-sharp is a tritone.

[00:03:22]So, now we know what a tritone is.

[00:03:24]You start on a note and if you go three tones away from it, you're dealing with a tritone.

[00:03:31]Sometimes people know the tritone as an augmented fourth or as a diminished fifth.

[00:03:37]So much of this depends on, you know, which tradition you've come through in your learning of music.

[00:03:43]But if it's C to F-sharp, it's an augmented fourth.

[00:03:46]If you've notated it differently as C to G-flat, it's a diminished fifth.

[00:03:52]Either way, it's a tritone.

[00:03:55]And it's interesting that back in mediaeval days when people were very superstitious, they talked about the tritone as the devil in music.

[00:04:05]I think it just has such a haunting sound, doesn't it?

[00:04:09]When you go around in tritones, it's a very haunting sound.

[00:04:12]And I think they thought there was something a bit sinister about it.

[00:04:16]So, they thought it must represent the devil in music.

[00:04:19]So, there we are.

[00:04:20]So, it's been around for a long time causing its own history of trouble.

[00:04:24]But as you can hear, it's a very powerful interval.

[00:04:28]And tritones normally have a resolution.

[00:04:32]They pull in a particular direction.

[00:04:34]So, if I have C and F-sharp, quite often they kind of pull outwards.

[00:04:38]So, the C falls to B, and the F-sharp rises to G.

[00:04:42]So, you can hear that tritone has a resolution.

[00:04:46]If I call it C to G-flat, often it pulls the other way.

[00:04:50]So, the C pulls up to D-flat, and the G-flat pulls down to F.

[00:04:54]So I get that.

[00:04:56]Now, when you hear a tritone like that, it kind of has a context that we're familiar with.

[00:05:02]We've sort of heard that sort of thing happening.

[00:05:04]So, it's possible to have a tritone that even though it sounds a bit stark and a bit sinister, you can kind of resolve it in one of those ways.

[00:05:12]Okay, well we're gradually kind of building up to what the chord is about.

[00:05:16]But before we get to that, well, why is it called a substitution?

[00:05:20]Well, what's it substituting?

[00:05:24]Well, let's think about this for a moment.

[00:05:26]If I was in the key of C major, and I wanted to put a chord before a C major chord, quite often I would put a G seven chord, or what we sometimes call a V7 chord, because it's a really good chord to put before chord I in C major or a C major chord, because it kind of pulls you on there.

[00:05:48]So, if I go G seven and then C major, that's a really good strong move.

[00:05:56]And inside that G seven is this tritone.

[00:05:59]Do you hear that tritone?

[00:06:00]And it's kind of pulling me into a resolution.

[00:06:03]So, that V7 to I, or that G seven to C is a progression that it comes up in music of all styles and all periods.

[00:06:14]So, it's great.

[00:06:16]So, if we get to what would be a tritone substitution in C major, let me tell you that the chord would be D-flat seven.

[00:06:28]Now, you might be thinking, why would I want to use a D-flat seven chord when I'm in C major?

[00:06:34]Well, remember what we said about it's a non-diatonic chord.

[00:06:38]So, even D-flat, you immediately think, well, D-flat isn't in the key of C major, no, because it's a non-diatonic chord.

[00:06:47]Okay, now why would I want to use a D-flat seven as some kind of substitution for a G seven, because we're really happy with our G seven going to C, aren't we?

[00:06:58]But, I mean, it gets used a lot and sometimes we might think, another G seven going to a C, could I vary that G seven, do something else?

[00:07:07]Well, let's have a think about how that D-flat seven could be a substitute for a G seven.

[00:07:15]And there's two kind of reasons, really.

[00:07:17]And the first is this.

[00:07:18]Inside any dominant seventh, you've always got a tritone.

[00:07:23]So, when we did that G seven, remember we talked about the tritone, didn't we?

[00:07:27]B to F, there's a tritone in there.

[00:07:31]And any of these intervals, or any interval in music in fact, can be inverted.

[00:07:36]In other words, you can turn it upside down.

[00:07:39]So, if I've got B at the bottom and F at the top, I could turn that upside down, couldn't I?

[00:07:45]So I could call it F and B, and if I turn it upside down, so B to F turns upside down to F to B, I could also say that that B is also called C-flat because every note has more than one name.

[00:08:01]I can call that B, but I can also call it C-flat because it's a semitone below C.

[00:08:06]So, if I have a D-flat seven chord, can you see what's happening?

[00:08:11]It's using the same tritone as that G seven chord, even though it's been inverted.

[00:08:20]I had this in the G seven, and now I've inverted it.

[00:08:24]And I've got that in the D-flat seven.

[00:08:28]And if I call it C-flat instead of B, it still sounds the same.

[00:08:32]But you see what I've done?

[00:08:34]I've taken the tritone out of the V7, the G seven, I've turned it upside down and then said, there's a tritone inside a D-flat seven.

[00:08:43]So, that's how that works.

[00:08:44]It's about the inversion of that tritone.

[00:08:47]They kind of belong to each other.

[00:08:50]And it's also interesting that I was talking about a G seven chord, and now I'm talking about a D-flat seven chord.

[00:08:56]It's also interesting that D-flat is a tritone away from G.

[00:09:02]If I've got G, and then I go to D-flat, that's a tritone.

[00:09:06]One tone, two tones, three tones.

[00:09:10]So you see how this tritone thing plays out in two different ways really.

[00:09:17]Okay, so what's the easiest way to find the tritone substitution chord in any given key?

[00:09:26]Because you could use the information that we've just shared together, but you might be thinking, oh my goodness, I've got to find this G seven thing, and then I've got to find the tritone, then I got to turn that upside down, and then I've got to call that something else.

[00:09:39]And oh dear, this is all too much.

[00:09:42]That will work, I mean, you'll get there.

[00:09:44]And the information I've just given you explains why it's a tritone substitution chord.

[00:09:51]But if you just want to find the chord quickly, well, you could do it another way.

[00:09:56]So, let me explain how you could do that.

[00:09:58]First of all, you start from your tonic, in other words, your first note of the scale.

[00:10:03]So, if you're in C major, your tonic is C, okay?

[00:10:07]So, you start with C, the tonic, the first note of the scale, and then you're going to try and build a chord on flat-two.

[00:10:17]So, if I'm in C major, well the second note is D, so the flat-two is D-flat.

[00:10:25]So, either by saying, well, C's the first note, D's the second note, so flatten it to D-flat.

[00:10:31]Or think, well, I'm starting on C, go up a semitone, D-flat, doesn't matter which way you do it.

[00:10:36]And then build your seventh chord.

[00:10:37]So, D-flat, F, A-flat, that gives you a major chord.

[00:10:43]D-flat, F, and A-flat, then add your C-flat.

[00:10:48]We called it B when we were doing G seven, but let's call it C-flat, doesn't really matter at the moment, really.

[00:10:54]And you've got your tritone substitution.

[00:10:57]So, do you see how we got there?

[00:10:59]Just a slightly simpler way of doing it.

[00:11:01]You start with C, you go up a semitone, or you go to the flattened second to D-flat, you've got a D-flat chord, D-flat major chord.

[00:11:09]You add a seventh, the C-flat there, or the B, and then you've got your tritone substitution.

[00:11:15]That's the chord that's going to replace your G seven or your V7.

[00:11:20]And by the way, it works exactly the same in minor keys as it does in major keys.

[00:11:24]So, if you wanted this to be a tritone substitution in C minor, it works just as well.

[00:11:31]So, how are you going to use it?

[00:11:33]Well, we've got common progressions in music.

[00:11:36]So, you might have a progression, for example, that goes II-V-I.

[00:11:43]Let's just put that in another language.

[00:11:45]If we're in C major, it would be a D minor chord, a G chord, and a C chord.

[00:11:51]So, II-V-I.

[00:11:54]So, D minor, G, C.

[00:11:58]Okay, now you could make that a bit richer by adding sevenths.

[00:12:02]So, I could go II, or D minor, V7, or G seven, I.

[00:12:10]I could add another seventh by using a seventh on the first chord.

[00:12:13]So, II7, or a D minor 7, V7, or a G seven, and then I, the C chord.

[00:12:21]Okay, now how about you replace the V7, or the G seven, with the tritone substitution.

[00:12:30]So, I now go II7, or the D minor 7, and then I'm going to use this D-flat seven chord, and then go on to C, or could even be a C major seven chord, you know?

[00:12:47]And then I could use that and then use a C major seven.

[00:12:54]Just gives you more colour, doesn't it?

[00:12:57]Now, some people watching this, they're going to say, "Hang on a second, that D-flat, F, A-flat, C-flat chord, "well, that's actually a V7, "or a dominant seventh in G-flat major, isn't it?"

[00:13:11]Absolutely correct, you're right.

[00:13:13]It's fine because it can function as a V7 in G-flat major.

[00:13:19]So, I could use that and then go to G-flat major.

[00:13:23]Or it can function as a tritone substitution in C major.

[00:13:30]So, this is why it's such a useful chord.

[00:13:31]It's very flexible, very colourful.

[00:13:34]And other people might be saying, "Hang on a second, if I've got this chord "D-flat, F, A-flat, B, "that looks like a German sixth to me."

[00:13:45]That's true, actually.

[00:13:46]And it may be seen as a German sixth in the key of F major because we normally build a German sixth on a flat-sixth degree of the scale.

[00:13:56]So, a German sixth is often referred to as a pre-dominant chord.

[00:14:01]So, if we had that as a German sixth in the key of F, it would usually resolve to chord V in F, which is a C major chord.

[00:14:10]So, it's doing exactly the same as the tritone substitution.

[00:14:14]So, that's quite interesting as well.

[00:14:17]And of course you can have a German sixth built on flat-two as well as on flat-six.

[00:14:21]So, it's all about different conventions.

[00:14:24]And if you're thinking, German sixth, what the heck's that?

[00:14:26]Never heard of it.

[00:14:27]Doesn't matter at all.

[00:14:29]But I'm just making this link for people who perhaps have never heard of a tritone substitution, but have heard of a German sixth.

[00:14:36]Or people who are not sure what this is, but they know about a D-flat seven chord relating to G-flat major.

[00:14:42]It's just to make the point that, yeah, these things can function in different ways in different circumstances, but it's all amounting to what we're talking about here, the tritone substitution.

[00:14:54]So, you know, the great thing is there are musicians around from so many different musical traditions, working in different musical genres, that's fantastic.

[00:15:03]And, you know, we want to be open to all, that's great.

[00:15:06]So, we sometimes have slightly different language for explaining the same things.

[00:15:11]And we sometimes use the same things in slightly different ways.

[00:15:14]But hey, non-diatonic chords add colour.

[00:15:18]So, it doesn't matter if you're playing in a rock band or you're looking at some of this stuff in Mozart, non-diatonic chords are a way of adding colour, a way of adding variety, a touch of something less expected.

[00:15:32]And as with all these things, you know, once you've got your head round what a tritone substitution is and how it works, what it sounds like, play around with it.

[00:15:42]Just keep playing them.

[00:15:43]You know, build them into your writing until you get happy about using them.

[00:15:48]And you'll find it's a great way just to add a bit of colour to what you're doing.

[00:15:53]So, I hope you enjoy working with tritone substitutions.