I thought it was worth blogging my answer to this question asked on 'Customer Questions & Answers' on my Amazon product page:
Question: How is this different from a chord wheel?
The short answer:
Think of The Mode Decoder as a chord book and solo guide all rolled into one - with extras!
For all diatonic keys and their modes (all 84), the Mode Decoder shows visually:
1. The main major and minor chords plus the half diminished chord
2. Additional chord variations (with ‘easy bar chord’ diagrams on reverse.)
3. Chords are in sequence I ii iii IV V vii viii
4. Solo with the minor pentatonic and minor scale in any key/mode
5. Focus on modal character / target notes both for chords and solo
6. Transpose keys easily or transpose a song between modes - make a sad song happy!
The long answer:
There’s so much more to the Mode Decoder than a regular chord wheel. Because it is a visual system, you don’t need to learn any theory or do any working out to be able to see which chords go together and you don’t need to learn all the modal scales either - just use the regular minor pentatonic scale (and optionally the full minor scale) for all keys and modes.
The Mode Decoder will show you not only what chords are major and minor (and half diminished), but also a handful of variations for each . For example, as well as C major, you can see that Cmaj7; C6; Csus2; Csus4 and a C5th powerchord are all playable in the Key of C major (there are simple bar chord diagrams for all these chords on the back page). Simply use one of these alternative chords in place of the main chord to instantly sound more jazzy or to add colour and light and shade to your playing and composing. Additionally, these chords are colour coded so you can see instantly which ones go best with each mode you are in e.g. if playing or composing in Mixolydian, try choosing the chords marked with a blue dot first.
On the inside, The Mode Decoder will show you which frets to start the minor pentatonic and minor scale pattern so that all the notes are within your chosen key or mode. There are 3 places the minor pentatonic scale will fit and a further possible 3 past the 12th fret for all diatonic keys and modes of these keys (That’s 84 scales). So you can easily solo up and down the guitar neck in up to 6 places in any key or mode using only the minor pentatonic (and optionally, the minor scale).
Unlike a normal chord wheel which is usually based on the circle of fifths diagram, The Mode Decoder is set out in a logical sequence from I ii iii IV V vii viii . This makes transposing easy by just counting. If you have a song in C major with the structure I IV V (C F G), you will see C in the first window, F in the fourth window and G in the fifth window. To transpose this from a major (aka Ionian) progression to be a C Dorian progression for example, just turn the Mode Decoder so ‘C’ is in the Dorian window and then count 1,4,5 to reveal the new chord progression (cm F gm). Great fun for changing the sound of well known songs! You can also easily transpose songs in the traditional way eg to transpose the above to F, just put ‘F’ in the window that C was in (The Ionian) and count 1,4,5 again (F Bb C). Because it is sequenced in a line from 1-7, this also works very well with Nashville Numbers.
I created the Mode Decoder for myself and out of necessity because I didn’t and still don’t have much time to play. I was frustrated that all that time was mostly taken up trying to learn a particular song or scale. Then, once I had learned something, I had to remember it and by then I probably felt like learning something else! My skill level was and is quite low - I can play a handful of chord shapes, cowboy style and bar chord style plus the minor pentatonic scale. Because my job is being a graphic designer, I had the skills to design this product and get it printed and constructed - so that’s what I did 3 years ago. Since then I have been selling on Amazon and taking it to guitar shows around the UK. The response has been fantastic and many have fed back to me with feedback such as “It was a game-changer for me’ and “A light went on and I could suddenly play along to any track”
The Mode Decoder is a compact, but a very powerful way to ‘see’ music and is useful as an aid for writing and analysing songs and for enabling you be able to to solo to most songs without hours of learning scales or music theory! Eventually, you won’t need to even find the key - just find where the pattern fits! Its a must-have because it remains useful whatever skill level you achieve.