SO FAR IN THESE articles, you've been playing the musical ideas "blind", accepting my voicings of the chords and the bass lines I've chosen for you. Obviously, I could go spoonfeeding you with chord progressions and styles, but this wouldn't encourage you to develop your own ideas on the guitar.

The best place to start with technical detail is on the bass lines you choose to play with a particular chord. You will remember that I have used examples of simple fingerstyles and plectrum techniques, both of which have centred around the idea of playing a reasonable bass line. I want to carry on that process this month, but this time introducing some basic musicianship ideas which will allow you to make some judgements of your own about which notes to play in a bassline for any given chord.

If you have been very good and bought the magazine every month, you will have read the Key Lines articles along with this one, so what follows will be a reminder of some of that information. If you haven't read the other articles, take a slap on the wrist, and if you haven't bought all the issues of the mag... well... what can I say! Other than that the editor is sending a squad of heavies round right now...

Seriously, there is very little technical detail to understand about chord construction — it's simply a question of being organised. Here's the familiar C major chord shape I've used for a while now (Diagram A).

How many different notes (by letter name) in the chord? Only three: C E G. This is the first detail — the simplest chords have only three different notes, identified by letter names (these chords are called triads). Notice in this version of C, there are two Cs and two Es an octave apart from each other.

What about the G7 chord used recently (Diagram B)?

There are four different notes in this one: G B D F. Why? And where do the notes come from to construct these chords?

First, all chords relate to some form of melodic organisation of notes — what we usually call a scale, which is really a succession of notes identified by different letter names, as shown in Diagram C.

That's a C scale, shown using notation and letter names and a box, so you should be able to grope your way round that, Now go back to the C chord, and you'll see that it uses three notes of the C major scale — C E G, — by counting from the lowest note, three and five letters away from the C. If you start the G7 chord on G, and count three and five letters away you get G B D, and F is seven letters' count away. Simple enough? Here it is in real notation and letters (Diagram D).

You will notice that the chords are named by the lowest note used in this organisation of sounds — in this form the chords are in "root" position, and C is the root of C major, G is the root of G7. Obviously, you could build a chord on each note of the C major scale, and following the pattern of thirds and fifths away from the root chosen come up with a set of chords. Diagram E shows this process in action.

This is the set of chords for C major, using only the notes of a C major scale (this is called a diatonic scale). Why the extra note on the G7 chord? Simply because composers used it so often that eventually everybody associated it with the chord built on the fifth degree of the scale. What is so brilliant about this language is the regularity of it. Play the two scales (C and G major) shown in Diagram F.

You should be able to tell that those are the same ideas, but produced at a different pitch. The scales are the same because the steps between each note are exactly the same in terms of "tones" (two frets on your guitar) and "semitones" (one fret). The major scale — any major scale will happen — if you produce:

tone / tone / semitone / tone / tone / tone / semitone

Try using letter names only. Start on A, then E, then F, as in Diagram G.

Convinced? You should play this until you have convinced yourself that these are the same ideas using different starting points, different pitch. If the scales are the same, then so must the chords be. Diagram H shows you how this works.

Enough technicalities. Next time, I'll give you a full list of scales and chords in a major key, so that you can be confident of finding your way around the ideas. Remember though, these are the musical ideas common to all of us, for any instrument or voice — we still have to translate them into guitar ideas, which is where the chord boxes come in. Play C and G7 again (Diagram I).

Which bass notes have I picked? Root and fifth, or root and third? Lo and behold, the structural notes of the basic triad we have been talking about! So on an A-E7 change (Diagram J), using the same sort of texture ideas, what bassline would you expect to play!

Yessir — root and fifth is much simpler for both these chords, because you don't have a third fingered in the left hand in the basic chord shape. More of all this next time, as we develop bassline runs and start to take off into, ahem, more interesting territory.

Remember though, if you're playing like a robot, not understanding, you won't go far forwards. The aim is for you to do the creating, not me.