Your instrument is tuned in 5ths, GDAE, (CGDA for mandola as well). This is no coincidence, as the interval of a 5th is an important one for Western European music. The 5th note of the scale is important as being a consistent chord tone, and we've refered to the Tonic/Dominant relationship in chord progressions in the past. The chord based on the 5th scale degree is the Dominant.

You can see from the Circle of Fifths diagram, we have a cycle where progressing clockwise, you go through all 12 keys, and eventually find yourself back where you started from, very much like a clock. Point of clarification, this is not meant to be a Circle of Fourths as one might observe (C up a 4th is F) going clockwise. What you have is a chord which is a 5th of the next key. C is the 5th to the key of F.

Let's examine why this diagram is important enough to internalize visually:

• 1. Knowing the 5th of the key at all times gives you the chance to move home, especially when the chord based on the 5th is a Dominant 7th chord. C7 will lead to F. F7 will lead to Bb, Bb7 will lead to Eb, etc. all the way around the clock.
• 2. Knowing a sequence of 2-4 fifths in the sequence provides you an opportunity to do "Turnaround" phrases. In Jazz and in the Blues, rather than staying on the tonic, you can work your way backwards with four chords in two measures by using the 5th, the 5th of the 5th, the 5th of the 5th of the 5th, etc. For example in the key of F, C7 will precede, G7 will precede C7 (it's the 5th of C), and D7 will precede the G7 (it's the 5th of G). The chords in an F Major "Turnaround" will be F, D7, G7, C7, two beats to a bar, and you're ready to start in the home key again.
• 3. Learning your key signatures is much easier with the chart. Start with C and going clockwise you add a flat. Next key Bb is two flats, and Eb is three. Now start with C and go counter-clockwise, you add one sharp to get G. Add two you get D, and three you get A, all through around the circle.
• 4. Note at the bottom of the circle you get that "Netherworld" of five flats, six sharps, etc. Though they aren't listed above, you have the enharmonic equivalents of B (Cb), F# (Gb), and Db (C#). These don't have to be tricky if you spend some quality time in these keys, and know these relationships intellectually. (This is why we stress playing in all keys!)



• 5. Your "tritone" relationship is always directly across the clock. The farthest point away will be that magic opportunity for tritone substitution chords. C is the F# tritone; A is the Eb tritone.
  

Always be ready to take the Fifth...