Here is an example of some 'Mexican' sounding guitar. We all know the sound of it -- warm and friendly, tropical breezes and sand between the toes -- now let's analyze it and see what makes it so distinctive. This short example has no title, belongs to no tune ... it's really just a chord progression, played à la South-of-the-Border.

The chord progression: you can probably hear that it's very 'major' sounding. There are no 'blue' notes, no hint of anything jazzy. The chords are all key related, based around the I-IV-V (as usual), with a vi chord thrown in (that Bm) and a dash of diminished as a passing chord. Here it is in Roman Numerals:

| IV V I - | IV V iii^dim I | IV V I vi | IV V I - |

Which, in the key of D, means:

| G A⁷ D - | G A F^dim D | G A D Bm | G A D - |

So there's not really that much to it chord wise, but it's the voicings and one particular harmony that give the progression that sunny feel. The main ingredient is the use of harmony lines in sixths. The most common way to harmonize a melody is to create a new line a third above the original, 'third' meaning 'use not the next in the scale, but the one after that' ... it's a little confusing, but the original note is considered the 'first', then there's the one you DON'T use, the 'second', then the next scale note, the 'third', is the one to use. Of course, because the scale is not symmetrical, the distance between any note and its harmony note is not constant. The only way I know to keep track of these harmonies is to keep the chord in mind, not the scale.

So that's thirds, 'sixths' are 'thirds' measured backwards, so you wind up with the same two notes, but the harmony note is in the octave below. It is that sound that is the 'South of the border' sound. Sixths are never played on adjacent strings, they skip a string. In this example, some of the sixths are part of the chord, so it's not one continuous parallel harmony line, but I do that to add interest to the ear.

From the top: The example is introduced by an ascending bass line from the I, the root, up to the IV chord. The picking hand is kept busy switching between various plucking configurations. The sixths come into play at the A7 abd D of bar 2 and at the repeats in later bars. As always, the thumb is underpinning everything with a simple bass line, mostly roots. The timing also contributes to the Caribbean 'feel', the way some of the bass notes insert themselves off the beat. The details of this can be found in the tab below.

The main thing to keep in mind are the I-IV-V chords in all their positions. This may sound like a big ask, but it's not all that difficult to do if you know the trick. Once you can visualize those three 'primary chords' (and this applies to all music, all style), you have pretty well mapped out ALL the potential of the piece: all the thirds, sixths, fifths; all melody, scales and modes. I'm not exagerrating when I say that detailed knowledge of the the I-IV-V chords automatically keeps everything on track within a key.

This little piece is good pratice for your picking hand, as it never settles into any one pattern. Patterns are good too, but getting your hand to do whatever you want it to do whenever to tell it to is a lot trickier and requires a lot more practice.

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