Tag Archives: free bass lessons

Pentatonic Jazz Exercise – Bass Practice Diary 106

Inside/Outside Pentatonic Jazz Exercise for Bass Guitar – Bass Practice Diary – 5th May 2020

This week I’m featuring a pentatonic jazz exercise that I came up with. Since I released my pentatonic jazz lick video a few weeks ago, I’ve been coming up with exercises to help me play these inside/outside pentatonic ideas all over my bass and in different keys. I’m featuring the exercise for two reasons. One is because it’s a useful exercise to practice, but the other, more important reason, is to help you come up with exercises of your own by sharing my process with you. This is how I came up with the exercise.

A minor pentatonic exercise

An idea for an exercise usually starts with something very simple, and then I find ways to make it progressively more challenging. In this case, I started with the notes of an A minor triad. Then I took those three notes through the notes of an A minor pentatonic scale by moving each note one scale step downwards on each repetition. Like this.

A minor pentatonic triad exercise
A minor pentatonic triad exercise

Then I changed the feel from triplets to 16th notes. That created a three against four polyrhythmic feel. The pattern is three notes but each beat had four subdivisions.

Then I added the II-V-I inside/outside idea from my last pentatonic video. If you think of the Am triad as being chord II in a II-V-I in G major, then you would play two beats on A minor. Then two beats on D7 before resolving onto the one chord, G major, in the second bar.

Inside/Outside Pentatonic Jazz Exercise
Inside/Outside Pentatonic Jazz Exercise

The three scales used are A minor pentatonic on the A minor chord. The outside scale is Bb minor pentatonic on the D7 chord. And the exercise resolves onto B minor pentatonic on the G major chord. Three pentatonic scales separated by a semi-tone. Two of the scales contain entirely inside notes in the key of G and the other contains entirely outside notes.

6-String Bass Solo & Chords – Bass Practice Diary 103

6-String Bass Solo & Chords with Bass TAB & Chord Diagrams – Bass Practice Diary – 14th April 2020

This week I’ve transcribed a 6-string bass solo that I played in practice. It follows on from what I was doing last week, finding creative ways to use pentatonic scales in jazz solos. These days I often practice the same ideas on both guitar and bass. In this case I started by playing some pretty chords on the guitar. Then I came up with two pentatonic scales, a tone apart, that worked on each chord. So, each chord had a different pair of scales. I then tried to improvise lines on my 6-string bass using the two pentatonic scales plus a third outside scale that sits exactly between the two scales. Using this idea I was trying to create inside/outside jazz lines in the same way I did for my pentatonic jazz lick last week.

The Chords

Having done this I then switched it around. So, I worked out how to play the chords on my 6-string bass and I improvised solo lines using the same system on the guitar. Here are the chords and scales that I used in the video.

The first chord is Emaj9, and the two inside scales are C# minor pentatonic and D# minor pentatonic. The reason I chose those two chords is that I was thinking of the Emaj9 chord as lydian, and those two scales spell out the E lydian sound very well. The outside scale would have been D minor pentatonic, but I didn’t use it on the solo I included in the video.

I then played a sequence of major chords over a peddled E bass note. D/E creates an Esus chord and I used the B & C# minor pentatonic scales and C minor pentatonic for the outside notes. Then on C/E I used A & B minor pentatonic and Bb for the outside notes and then A/E I used F# & G# minor pentatonic and G for the outside notes. In each one of these slash chords I was thinking of the major chord as being lydian.

Finally I played an Em9 chord which I treated like a II-V-I in D major, exactly as I did last week. In fact, I tried to used the lick from last weeks video on this chord. I didn’t execute it perfectly but the idea still came across.

The Solos

These solos are a long way from being perfect, they represent what I’ve been working on this week, which is the point of my bass practice diary. I’m including the transcriptions here to help you see my thought processes as I tried to create these lines. But I’m sure that you can take these ideas and improve on what I’ve done, which is what I’m going to do as well. It’s actually a great exercise to transcribe your own solos, because you can immediately think about how you would do it better next time. Here is the bass solo I played in the video.

6-string Bass Solo featuring Inside/Outside Pentatonics
6-string Bass Solo featuring Inside/Outside Pentatonics
6-string Bass Solo featuring Inside/Outside Pentatonics

Here is the guitar solo.

Guitar Solo featuring Inside/Outside Pentatonics
Guitar Solo featuring Inside/Outside Pentatonics

Pentatonic Jazz Lick – How to Use the Pentatonic Scale in Modern Jazz Part 1 – Bass Practice Diary 102

Pentatonic Modern Jazz Lick – Bass Practice Diary – 7th April 2020

This week I’ve written a pentatonic jazz lick to try and demonstrate how pentatonic scales can be applied to modern jazz. If you think that pentatonic scales are just easy scales for beginners then you need to read this. I think Google and YouTube probably need to read this as well, because when you search for pentatonic scales, you get a lot of content that is targeted at beginners.

The Pentatonic Scale

Pentatonic means five notes. So, you could technically have any number of different five note scales that could be labeled pentatonic. But there is one pentatonic scale which is “the” pentatonic scale. The same scale can be used for both major and minor and it goes like this.

A minor/C major Pentatonic Scale

It’s an incredibly useful scale because pentatonic melodies are universal. I can’t think of many styles of music that don’t use pentatonic melodies. They have a very distinctive character.

Many people associate pentatonic melodies with blues guitar playing. But the applications of pentatonic melodies go way beyond blues licks. Not that there’s anything wrong with playing blues lines. Blues melodies and phrasing are hugely important in jazz, and blues phrases played well can be both beautiful and sophisticated.

However, it’s possible to approach pentatonic melodies in a completely different way. And that’s what I’m looking at this week.

One of the great strengths of the pentatonic scale is it’s versatility. If you’re only using the scale one way, then you’ve missed part of the point of them. If you take any major key, then you always have three different pentatonic scales within that key. Using the key of D major as an example, you have B minor/D major, E minor/G major and F# minor/A major pentatonic scales all within the key. Each creates a different sound played against a D major chord.

Pentatonic Jazz Lick

My pentatonic jazz lick uses three pentatonic scales in the key of D, but none of them are D major pentatonic. I’ve used E minor pentatonic scale on the Em7 chord, which is chord II, and I’ve used the F# minor pentatonic scale on Dmaj7, chord I.

The other scale that I’ve used is F minor pentatonic. This is a scale which gives you all of the notes that are not in the key of D major. I’m using this scale on an A7 chord, chord V. Why play a scale that uses all the outside notes? To create tension that can be resolved on the one chord (Dmaj7).

Of the five notes in an F minor pentatonic scale, F, Ab, Bb, C & Eb. Four of those notes are altered extensions on an A altered dominant chord, b9, #9, b5 & b13. The other note is Ab. That’s not a note you want to feature too prominently on an A7 chord, because it’s a major 7th on a dominant chord. You can use it, but you have to be careful how you use it. I’ve used the Ab once in my lick and it’s the last note before resolving to chord I. The Ab functions as a chromatic approach note leading to A natural, which is a chord tone in the Dmaj7 chord. Here’s the lick.

D major II V I pentatonic jazz lick

Superimposing II V I Licks

I’ve written the line above onto a II V I in D major. But I wouldn’t necessarily choose to play the lick in that context. When I came up with the lick, I was thinking about it more as a straight 1/16th note feel on a funky modal idea.

Jazz musicians love to superimpose II V I lines onto individual chords. You could play that entire lick on a single Em7 chord or Dmaj7 chord or A7 chord.

Pentatonic Jazz Lick
Pentatonic Jazz Lick

You could even play it on a G major chord and it would create an inside/outside lick with a lydian sound.

Triad Pairs – Part 3 – Triad Pairs & Hexatonic Scales – Bass Practice Diary 96

Triad Pairs – Part 3 – Triad Pairs & Hexatonic Scales on 6-String Bass – Bass Practice Diary – 18th February 2020

This week I’m exploring the connection between triad pairs and hexatonic scales. My two previous Triad Pairs videos have featured major triad pairs on 4-string bass. This week I’m opening it up to include all types of triads. And I’ve switched onto my 6-string bass because I would most commonly use these kind of ideas on my 6-string.

What are hexatonic scales?

Hexatonic scales are simply scales that have six different notes. The term hexatonic doesn’t get used that often, except in the context of quite advanced jazz improvisation. But hexatonic scales are actually a lot more common than you might think. Probably the most obvious example of a commonly used hexatonic scale is the blues scale. Another common hexatonic scale is the whole tone scale.

Hexatonic scales
Whole Tone Scale – Starting on C

The C whole tone scale above is comprised of the notes of a C augmented triad and a D augmented triad.

C and D Augmented Triad Pair

Minor triad pairs

Having explored major triad pairs in my first two videos, the next most obvious triad pair would be two minor triads separated by a whole tone (2 frets). You can think of these as chords II and III in a major key. For example these two triads, Dm and Em, can be used to play lines in the key of C major.

D and E minor Triad Pair

You can also find two minor triads a tone apart in the melodic minor scale. The altered scale is a mode of the melodic minor scale. I demonstrated in the video how you can create an altered scale sound on a C7 chord by using Db minor and Eb minor triads.

Db and Eb minor Triad Pair

Combining different types of triads

The idea of triad pairs, as I’ve mentioned previously, is to find two different triads that give you six different notes. Those two triads don’t have to be the same type of triad. In this next example, I’m playing an E augmented triad and a G major triad. This triad pair also creates an altered scale/melodic minor sound.

E augmented and Gb major Triad Pair

The Augmented Scale

Another hexatonic scale created by combining two augmented triads is the augmented scale.

Hexatonic Scale
Augmented Scale – Starting on C

The augmented scale is comprised of the notes of two augmented triads a semitone apart. In this case, C augmented and B augmented.

C and B augmented Triad Pair

These examples only scratch the surface of everything that you can do with triad pairs. Any time you can find two triads that give you six different notes, you have a triad pair. And those six notes can be played as a hexatonic scale. Practice my examples and see if you can find some more of your own.

Diatonic 7th Arpeggios in C major – Bass Practice Diary 95

Diatonic 7th Arpeggios in C major – Bass Practice Diary – 11th February 2020

In this video I’m playing all the diatonic 7th arpeggios in the key of C major on my 6-string bass. Exercises like this are ideal for learning how to play in any key, in any position on the fretboard. C major is the easiest key to demonstrate this in, because it has no sharps or flats. However, once you can do this in C major, it’s easy to transpose into other keys. And you should practice it in different keys.

What are diatonic 7th arpeggios?

Diatonic 7th arpeggios is just a fancy name for a simple idea. 7th chords are chords with four notes, root, 3rd, 5th and 7th. Diatonic 7th chords, just means all of the 7th chords you find in a particular key, like C major in this example. And these arpeggios are just those chords played one note at a time.

Chord I in the key of C major is Cmaj7, which includes the notes C (root), E (3rd), G (5th) and B (7th). You build these arpeggios by taking alternate notes of the C major scale, 1, 3, 5 & 7. Chord II is formed by taking the 2nd (D), 4th (F), 6th (A) and 8th (C) notes of the C major scale. These four notes create a Dm7 chord, and the pattern carries on for the remaining 5 chords in the key of C major, which are Em7, Fmaj7, G7, Am7 & Bm7b5.

Diatonic 7th Arpeggios in the Key of C Major
Diatonic 7th Arpeggios in the Key of C Major

I’ve arranged the arpeggios with the 7th as the first note, rather than the root. I’m only doing this because I like the way it sounds. And there’s no rule that says you must always play arpeggios starting on the root note.

Find my guide to playing minor scales on bass guitar in this video.

Triad Pairs – Part 2 – Using Major Triads to Improvise – Bass Practice Diary 93

Triad Pairs – Part 2 – Major Triads and How to Improvise on Chord Changes – Bass Practice Diary – 28th January 2020

A few weeks ago I introduced the idea of using Triad Pairs to make bass lines. This week I’m going to take that idea a step further by showing you how you can use pairs of major triads to improvise on chord changes. The idea with triad pairs, is to find two triads that have no notes in common, so you have six different notes. You can then use those notes to create exercises, melodies, bass lines or hexatonic scales (six note scales).

I remember when I first heard about the idea of triad pairs, it seemed to me at the time like the idea would have limited use. But when I got into it, I realised that the potential and the scope of triad pairs for creating interesting lines and harmonies, is absolutely massive.

Major triad pairs

There’s only three different ways that you can arrange two major triads and get six different notes. You can take two triads that are a semi-tone apart, a tone apart or a tritone apart. That doesn’t seem like many different options, but in a way, that’s part of the brilliance of triad pairs. You only need to practice those three simple ideas, and you suddenly have access to a massive amount of potential harmonic and melodic ideas.

Here’s an exercise for playing major triad pairs a semi-tone apart.

C and Db Major Triads – A semi-tone apart

This next one is a similar exercise for playing triad pairs a tone apart.

C and D Major Triads - A tone apart
C and D Major Triads – A tone apart

Here’s an exercise for playing triad pairs a tritone apart.

C and Gb Major Triads - A tritone apart
C and Gb Major Triads – A tritone apart

How to use major triad pairs for improvisation

Of the three exercises above, the least versatile is the triads separated by a semi-tone. That’s not to say that they don’t sound great. Two major triads separated by a semi-tone creates a phrygian dominant sound that instantly makes me think of Spanish music and Flamenco guitar. It’s a great sound, but it’s quite rare to find opportunities to use it in jazz.

One of the main reasons why I choose Chick Corea’s Spain as the template for these examples, is because the F#7 chord which immediately follows the opening G major chord, is a perfect example of how you can use the phrygian dominant sound to maximum effect.

Here’s a sample line using an F# and a G major triad.

F#7 Chord – phrygian dominant sound

By contrast, the most versatile, but arguably less interesting sounding, is to play two major triads a tone apart. The versatility rises from the fact that there are two major triads a tone apart in the major scale (chords IV and V) and in the melodic minor scale. So, you can conjure the sound of not only both of those scales but also all of their modes, including dorian, lydian, lydian dominant and altered scale, just by using two major triads a tone apart.

The example that I used in the video, was using Eb and F major triads on the chord V, A7 chord. Which is creating the sound of the altered scale.

A7 Chord – Altered Scale Sound

Then on chord I, D major, I dropped both of those triads by a semi-tone (one fret down). And the D and E major triads created a lydian sound on the D major chord.

Dmaj7 Chord – Lydian Sound

Altered dominant sounds

Two major triads separated by a tritone creates a kind of altered dominant sound. It’s not quite the same as using the altered scale, but what it gives you is two very different sounding triads. A and Eb major triads could be used to play on an A7 chord, as I demonstrated with the A7 in Spain. However, you could also use those same triads to play on an Eb7 chord.

A7 or Eb7 chord - A and Eb major triads
A7 or Eb7 chord – A and Eb major triads

What you get is one triad that is the root, 3rd and 5th of the chord. Those are the most obvious inside notes that you can play on any chord. While the other triad functions as 7th, b9th and #11th. Which is one chord tone and two altered extensions or outside notes. You can use this strange juxtaposition of inside and outside sounds to create some really interesting jazz lines on a dominant 7th chord.

Minor Scales on Bass Guitar – Bass Practice Diary 92

Minor Scales – Melodic Minor, Harmonic Minor, Natural Minor & Dorian – Bass Practice Diary – 21st January 2020

If I ask you to play a C minor scale, what do you play? Minor scales are not as simple as major scales. Most of us know what to play if someone asks us to play a C major scale, but minor scales are confusing. There are several different minor scales, and how do you know which one to play and when.

How many different minor scales are there?

If you’re going to understand minor scales, then it’s important to understand the difference between three different scales, melodic minor, harmonic minor and natural minor. Every scale is a sequence of intervals, and for each of these three scales the intervals are the same for the first five notes. It’s the 6th and 7th notes of the scales that contain the variations.

The terminology of minor scales confuses people for the simple reason that classical musicians treat minor scales differently from jazz musicians. To help explain this I’m going to start by looking at the natural minor and the melodic minor scales. I’ll use the key of A minor because it’s the simplest, it has no sharps or flats, so the natural minor scale contains the notes A, B, C, D, E, F & G.

Minor Scales - A Natural Minor
A natural minor scale

The A natural minor scale contains all of the same notes as a C major scale. That means that the natural minor scale is actually a mode of the major scale. It’s mode six, called Aeolian. Now, compare that to the melodic minor scale.

The melodic minor scale

Minor Scales - Melodic Minor
A melodic minor scale

The melodic minor scale has a raised 6th and 7th, meaning F# instead of F natural and G# instead of G natural. It’s important to understand that the melodic minor scale is not a mode of the major scale like the natural minor. It’s a parent scale and has seven modes of it’s own. You can check out my video about the modes of the melodic minor scale.

So, the natural minor scale is mode six of the major scale and the melodic minor is a scale with it’s own set of modes. So, not only do these scales sound different, they are also very different in their application. The natural minor scale implies a minor 7th chord functioning as chord VI in a major key, while the melodic minor implies a minor chord with a major 7th functioning as chord I in a minor key.

This becomes more confusing when you learn that classical music treats both these scales as one scale. The melodic minor is the ascending version of the scale, and the natural minor is the descending version of the scale. And together these are called the melodic minor. You can play it on the bass like this.

Minor Scales - Classical Melodic Minor
Classical Melodic Minor Scale

The harmonic minor scale

There is another minor scale, which, like the melodic minor, is a parent scale to seven of it’s own modes. It’s called the harmonic minor and it has a minor 6th and a major 7th. That means that in the key of A minor, the 6th will be an F natural and the 7th will be a G#.

Minor Scales - Harmonic minor
A harmonic minor scale

The harmonic minor scale can also imply chord I in a minor key.

The Dorian Mode

I’ve included a fourth scale in my video. The dorian scale is another mode of the major scale, mode number two. The reason I’ve included it is because it’s a much more common choice of scale for improvisers playing on minor 7th chords than the natural minor scale. However, you wouldn’t use an A dorian scale to play on chord I in the key of A minor. You would use it to play on an A minor 7th chord functioning as chord II in G major. It goes like this.

dorian
A dorian scale

The A dorian scale contains a major 6th F# and the minor 7th G natural.

Introduction to Triad Pairs on Bass Guitar – Bass Practice Diary 90

Introduction to Triad Pairs on Bass Guitar – Bass Practice Diary – 7th January 2020

This week I want to introduce some basic triad pairs exercises. The basic concept of playing triad pairs on bass is that you take two triads (three note chords) that don’t have any notes in common. Meaning that you have six different notes. And then you use those triads to makes lines and exercises.

Why use triad pairs?

Triad pairs are now a really common concept in jazz improvisation. But it’s not only jazz musicians that use them. You can apply triad pairs to almost any genre of music. They work particularly well for improvisation, but you can also use them to write bass lines.

This week, I’m only going to introduce the most basic form of triad pairs. Which is when you take two major triads that are spaced a tone apart. The reason for spacing them a tone apart, is because the triads function like chords IV and V in a major key. So you can use these kind of lines in any major key by transposing the two triads to the notes of chords IV and V in the key.

The exercises

All of these exercises are played using the triads C major and D major. Which are chords IV and V in the key of G major. But that doesn’t mean that you can only use these in the key of G major. There are all kinds of interesting and creative applications of triad pairs which I’ll try and cover in my future videos.

There are three obvious ways to voice a triad (inversions). You can put the root at the bottom, the 3rd at the bottom or the 5th at the bottom. This first exercise demonstrates those three different inversions, which you need to learn really well if you’re going to get good at playing these exercises. Bar 1 uses the root position triads for both C and D and then bar 2 uses the 1st inversion and bar 3 uses the second inversion.

Triad Pairs - Exercise 1
Triad Pairs – Exercise 1

This next exercise uses a similar idea, but with triplets. So, you play three notes on each triad rather than four.

Triad Pairs - Exercise 2
Triad Pairs – Exercise 2

Finally, here is a pattern that plays four notes on C and then three on D.

Triad Pairs - Exercise 3
Triad Pairs – Exercise 3

The purpose of playing patterns like this one in exercise 3, is that it helps to make the exercise sound less like a pattern. If you’re playing triad pairs in an improvised solo, and you play three notes up and three notes down, like exercise 2. It will very quickly sound like you’re playing a repeating pattern. That’s ok if it’s the sound you want. But, if you want to make it sound less like a pattern, then a pattern with an odd number sequence (three then four) will create a less predictable feel when played as part of a solo.

PLAYING CHORDS ON THE BASS – PART 3 – TRIADS

I VI II V Chord Progressions – Part 2 – Bass Practice Diary 87

I VI II V Chord Progressions on 6-string Bass – Part 2 – Bass Practice Diary – 17th December 2019

This week I’m revisiting my introduction to I VI II V chord progressions on 6-string bass video. There are so many ways that you can alter and substitute chords in a I VI II V sequence. Jazz musicians will often alter and add to the progression so much, that it’s almost impossible to tell that it was ever a I-VI-II V progression in the first place.

Chord substitutions

There really aren’t any rules when it comes to substituting chords. There are certain standard substitutions that are very common, such as the tritone substitution, which I looked at in my last video. But, honestly, you can substitute any chord for any other one that you like the sound of. A lot of it depends on the musical context that you’re playing the substitution in, but also it comes down to opinion. What sounds interesting to some people, will sound odd to others.

This week I’m just going to take you through some familiar chord substitutions and additions to I VI II V’s. These examples go quite a bit further than the examples in my previous video. But, believe me, you can take these ideas much further out than this.

The I VI II V examples

I created this first example by taking the III-VI-II-V example from my previous video and turning all the chords into dominant 7th chords. I then applied tritone substitutions to the VI and II chords. Then I added whatever extensions and alterations that I liked the sound of.

III – VI – II – V – I chord progression with dominant 7th substitutions

Once you have four dominant 7th chords like this, you can come up with so many variations just by applying tritone substitutions.

My next example derives from the first example. I’ve simply turned the E7, Eb7 and G7 chords into II-V’s. Meaning that I’ve added minor 7th chords before each dominant 7th chord. Each minor 7th has a root note that is a 4th below (or a fifth above) the root note of the dominant 7th chord. I’ve altered the VI chord to make it a major 7th instead of a dominant 7th chord. This completes a II-V-I in the key of Ab major, which is a strange thing to find in a chord progression in C major, but it works!

I – VI – II – V progression with II – V substitutions

I VI II V Chord Progressions on 6-String Bass – Bass Practice Diary 84

An Introduction to I VI II V – Chords on 6-String Bass – Bass Practice Diary – 26th November 2019

I VI II V is possibly the most commonly used chord sequence in jazz. So, I think it’s time I started to look at how you can approach playing this simple but versatile chord progression on a 6-string bass. It’s been a few weeks since my last video about playing chords on 6-string bass. So, I’m bringing the series back this week with an important one.

Why is I VI II V so common in jazz?

That’s a question I used to ask myself a lot when I was younger. When you listen to the progression played in it’s simplest form, it’s not particularly interesting. It’s quite practical, because it has a nice cycle of fifths movement, with the VI leading to the II to the V and back to the one. So it can just go around and around, with the V always leading back to the I. It’s a nice cyclical chord movement that takes you back to chord I. And as such it’s very often played on the turnaround of a jazz progression.

In the standard chord progression, chord I is a major 7th chord, chord VI is usually played as a dominant 7th chord. Although if you harmonise the chords using the diatonic major scale it would be a minor 7th chord. The reason it’s usually played as a dominant 7th chord is because it acts as a chord V leading to the minor 7th chord II. And the real chord V is also a dominant 7th chord.

Here is my version of a standard I VI II V chord progression in the key of E.

I VI II V in the key of E major
I VI II V in the key of E

But to really understand why I VI II V is so popular, I think you need to understand a bit about how and when jazz musicians like to use it.

Chord substitutions

The first thing that you need to know about how most jazz musicians will use the I VI II V progression, is that they will try to find as many ways as they can to avoid playing the obvious chord progression. They do this by finding chord substitutions and adding extensions and alterations to the standard chords.

I often get people asking me to explain the concept of chord substitutions. But it’s a very difficult thing to do. Because the truth is, that you can substitute any chord with any other chord. The only restriction is what your ear will accept is a valid substitution. And that is a matter of taste and opinion. How much dissonance are you willing to accept?

However, if I was going to sum up the concept of chord substitutions in one short paragraph. I would say that you are looking for chords that have important notes in common with each other. Which brings me neatly on to the most common chord substitution in jazz, the tritone substitution.

Substituting dominant chords

Tritone substitutions can be performed on any dominant 7th chord. The principle is, that any dominant 7th chord shares two notes in common with another dominant 7th chord. Those notes are the 3rd and the 7th. In order to find the substitute dominant chord you need to find a root note that is an interval of three tones away from the root note of the original chord. If you’re not sure what I mean, check out my guide to playing intervals on the bass.

Take the example of the G7 chord. The root is G, there 3rd is B and the 7th is F. You can play it like this.

G7 chord on 6-string bass. Root, 3rd and 7th.

The tritone substitution would be Db7. The root is Db, the 7th is B (Cb) and the 3rd is F.

Db7 chord on 6-string bass. Root, 7th and 3rd

Here is the I VI II V chord progression played in C major using tritone substitutions on the two dominant 7th chords. I’ve also substituted chord III for chord one in the first bar.

III VI II V with tritone substitutions