Quick answer: Guitar Intervals: Learn to Play in Any Key is worth buying if you know some chords and scales but do not understand how they relate, or if key changes and number-based charts leave you lost. It is a practical theory guide built around interval recognition, chord construction, scale relationships, and the Nashville Number System, with the goal of helping you function comfortably in any key.
For many guitar players, theory feels confusing until one concept finally begins to organize everything: intervals.
That is the problem Guitar Intervals: Learn to Play in Any Key: A Guitar Theory Guide to Intervals, Chords, Scales and the Nashville Number System is built to solve. This review looks at what it covers, who it suits, and whether it is worth your money. Note that the book is written by Julian Hoover, the author of this site.
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What Is the Short Verdict?
Instead of giving players more disconnected chord charts and scale patterns, this book focuses on helping guitarists understand the relationships behind the music so they can function more comfortably in any key.
That is a different aim from most guitar books, which add to the list of things to memorize. This one tries to reduce the list by explaining what the shapes have in common.
For players who feel they have collected plenty of material without understanding it, that approach is the main reason to consider the book.
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What Does This Book Cover?
At its core, this is a practical guitar theory guide built around:
- Interval recognition
- Chord construction
- Scale relationships
- The Nashville Number System
- Playing and transposing in any key
Each topic builds on the one before. Intervals come first, because they are the foundation. Chords are then explained as combinations of intervals. Scales are shown as interval patterns, and keys as families of chords built from a scale.
The number system ties it together by giving you a way to describe any progression independently of key. For a preview of these ideas, read Guitar Intervals Explained and Nashville Number System for Guitar Players Explained Simply.
Why Do Intervals Organize Everything?
An interval is the distance between two notes. Every chord, scale, and key can be described in terms of intervals.
A major chord is a root, a major 3rd, and a perfect 5th. A dominant 7 chord adds a minor 7th. A major scale is a fixed pattern of whole and half steps. The 4 chord of any key is a perfect 4th above the 1 chord.
When you understand these distances and can find them on the fretboard, the separate facts you have memorized turn out to be connected. You stop needing a different diagram for every chord in every key, because you can build what you need. That is why interval study is often described as the point where theory starts to make sense. Guitar Intervals Book: The Fastest Way to Understand the Fretboard expands on this.
Why Does It Stand Out?
Several qualities distinguish the book from general theory texts.
It is written for the guitar. Intervals are shown as shapes on the fretboard, so readers can see and play each concept immediately. Many theory books present the same ideas in notation and leave the guitarist to translate.
It keeps the focus on use. The stated aim is to play in any key, and each concept is directed toward that skill. It also brings in the Nashville Number System, which is the practical language of bands and session players and is often missing from theory books aimed at guitarists.
Finally, it connects chords, scales, and keys instead of treating them as separate subjects. That integrated view is what many self-taught players lack. The Guitar Theory Concepts That Actually Matter for Real Players explains why these particular topics give the most return.
What Can You Do After Working Through It?
The value of a theory book lies in what it enables. A reader who works through this material should be able to do several things.
They should be able to find any interval from any note on the neck. They should be able to build major, minor, and seventh chords from a root without a diagram, and alter a chord by changing one note.
They should be able to name the chords of any major key, describe a song as numbers, and move it to another key. Those are the abilities that make a guitarist useful in a band, and they are what this book is designed to develop. How to Play Guitar in Any Key shows the method in action.
Who Should Buy This Book?
The book fits several kinds of players.
Beginner to intermediate guitarists who want a clear foundation will find the progression of ideas logical. Self-taught players who can play songs but feel unsure about why chords work will find the gaps filled.
Worship and church musicians will find it directly relevant, since they deal with key changes and number charts constantly. Players preparing to work with bands or singers will benefit for the same reason.
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It is also useful as a companion to shape-based study. If you have learned CAGED shapes or scale boxes, intervals explain what is inside them. CAGED System vs Guitar Interval Training compares the two approaches.
What Are the Limitations?
It helps to know what the book does not try to do.
It is not a chord dictionary or a song collection. It will not hand you a set of licks. Its subject is understanding.
It is not an advanced jazz harmony text, and it does not teach standard notation reading. Players seeking those will need other resources. Like any theory book, it also requires participation. Reading without playing will produce little change. The benefit comes from working through the material with a guitar and applying it to songs.
How Should You Use the Book?
Work in short daily sessions with your guitar in hand. Read a concept, find it on the neck, and play it in several places before moving on.
Apply each idea to music you already know. When you learn chord construction, label the notes of your familiar chords. When you learn numbers, convert a song and move it to a new key.
Review regularly. Interval shapes and chord numbers become automatic through repetition over weeks, so return to earlier sections as you progress. Ten focused minutes a day is enough to see steady improvement. Why Beginner Guitarists Stay Stuck for Years explains why this kind of study breaks plateaus.
👉 See Guitar Intervals: Learn to Play in Any Key on Amazon
How Does It Help in Church and Band Settings?
Live playing is where interval knowledge proves its worth. In church, the key of a song is set by the singer or the keyboard player, and it may change during the service.
A guitarist who understands intervals finds the 1 chord in the new key and immediately knows where the 4, 5, and 6 chords are. When a music director calls out a number, the player knows which chord is meant. When a song modulates up a half step, the whole pattern moves one fret.
The same applies in any band. Musicians who can hear a progression as numbers and play it in the requested key are easy to work with, and that is the practical outcome this book aims for. Transposing on the Fly with Confidence describes the skill in more detail.
Is Guitar Intervals: Learn to Play in Any Key Worth Buying?
Yes, if your goal is to understand the guitar and play freely in any key.
Players who are content to learn songs one at a time from charts may not feel the need. Those who want to know why chords work, follow other musicians, and handle key changes without stress will find the book addresses exactly those needs.
Its strengths are its practical, fretboard-based teaching and its inclusion of the number system. For the price of a book, it offers a structured route through the theory that matters most. For a comparison with other titles, see Best Guitar Intervals Book in 2026.
👉 Get Guitar Intervals: Learn to Play in Any Key on Amazon
Frequently Asked Questions
Is this book suitable for beginners?
Yes, particularly for beginners who already know a few chords and want to understand how music fits together.
Does it teach the Nashville Number System?
Yes. The number system is one of the core topics.
Will it help me change keys on guitar?
Yes. Playing and transposing in any key is the main goal of the book.
Do I need to read music to use it?
No. The concepts are taught on the fretboard.
Who wrote it?
Julian Hoover, a guitarist and educator with more than 20 years of experience playing in gospel churches, who also writes this site.
What Is the Final Review Verdict?
Guitar Intervals: Learn to Play in Any Key is a practical theory guide that organizes the guitar around one clear idea. It explains intervals, builds chords and keys from them, and connects everything to the number system that working musicians use.
For guitarists who want to move beyond memorized shapes and understand what they play, it is a worthwhile investment.
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