No sooner has Andy Honeybone got you hooked on two-note "intervals" than he's whisking you off to the land of chords and modes. Built for speed, this boy.

KEYBOARD PLAYERS HAVE IT EASY. No fretting, stopping, bowing or blowing; all the notes just sitting there to be sounded at a touch, and polyphonic as well.

Not that keyboard playing is undemanding, but the sound quality that can be produced by a raw beginner is far more acceptable than that of a novice wind, brass or string player. This head start extends to the study of harmony which is evidently hard work on a monophonic instrument. The multiphonic guitar is the keyboard's nearest rival in this area, but the limitation of hand span and six strings gives problems with clusters of close-packed intervals.

Having put you firmly in your place, let's get to the meat. To paraphrase an old adage, 'two's an interval, three's a chord'. Two notes form an interval and the 12 possible permutations were dished up last month. The addition of other notes transforms the lone interval into a chord, the simplest being a triad (3 note) built, for example, from the root, third and fifth notes of a major scale.

Let's be specific and talk about the chord of G major, comprising the notes G, B and D. Not very exciting, agreed, but let's just rearrange the notes B, D, G to give us something called the first inversion with the third (B) as the lowest note. A further inversion is possible with the notes in the order D, G, B. Try them — all this proves is that a major chord sounds much the same whichever way up it is played.

So what else can be done with this root position (G, B, D) G major chord? It can be made a minor by simply flattening the third by one semitone (lower the B to B flat). Hence, G, B flat, D is G minor and, of course, it stays that way for each of its inversions as does every other chord. I'm sure you knew all that, but let's hurry slowly.

The major chord was built by piling alternate notes from the major scale on top of the root note (G, miss out A; B, miss out C; D). This system of chord building is based on thirds: G to B is a major third and B to D is a minor third. Why? Because that's what intervals of five and four semitones, respectively, are called. The last instalment should have made this clear.

If third building is applied to each note of the major scale, the result is a series of chord types as follows: major, minor, minor, major, major, minor and diminished.

In the key of G (one sharp) the chords are G, A min, B min, C, D, E min and F sharp dim. You shouldn't have any problems with the naming of these chords: majors contain a major third and a perfect fifth; minors contain a minor third and a perfect fifth; diminished chords contain a minor third and a diminished fifth. The chords of the 'three chord trick' are all there — G, C and D (the root, subdominant and dominant) — and are known as primary triads which are the backbone of the scale. No points for guessing that the remainder are termed the secondary triads.

The choice of the key of G was deliberate. The addition of that one sharp in the key signature results in the same sequence of chords built on the major scale as would have been generated if the scale of C had been chosen which has no accidentals (sharps and flats).

It's easy to say 'big deal' when you've been brought up in these chromatic times, but in the Middle Ages such transposition would not have been possible (no accidentals in those days). Without that F sharp in the example above, a completely different set of chords would have resulted giving rise to a different mood. We're now touching on something called modality, and it results from the only way that the ancients had of affecting different musical colourings from what amounts to the 'white notes' of a piano. There are seven modes given by starting on a different 'white' note and named thus:

Ionian: CDEFGABC
Dorian: DEFGABCD
Phrygian: EFGABCDE
Lydian: FGABCDEF
Mixolydian: GABCDEFG
Aeolian: ABCDEFGA
Locrian: BCDEFGAB

Aeolian and Ionian were late-comers introduced in the 16th century, and Locrian wa never used because its basic triad was diminished. It's difficult to imagine a system whereby mood and pitch were inextricably mixed — rather like someone dictating that all jolly songs should be in the key of C major and all sad songs in the key of A minor.

With modern chromatic instruments it is possible to transpose the modes into any key we chose. For example: (C to C)

C Dorian: flatten B and E
C Phrygian: flatten B, E, A and D
C Lydian: sharpen F C
Mixolydian: flatten B
C Aeolian: flatten B, E and A

The Ionian mode is equivalent to our present day major scale and the Dorian is widely used in jazz playing. Modes have been explored pretty thoroughly by Coltrane, although perhaps Miles Davis' 'So What?' is a more palatable introduction. Model playing is a reaction against the barrages of chord changes much beloved by hard-boppers. The bass never moves away from stating the 'final' or root note of the mode. That's not to say it just plays one note but its main job is to underpin the harmony which swims around on top.

A spot of practical now, a Mixolydian adventure. If third building is applied to the notes G-G (F natural this time) the following harmonies are given:

G major G bass = G
A minor G bass = G69sus4
B dim G bass = G7
C major G bass = C second inversion
D minor G bass = G9
E minor G bass = G6
F major G bass = Gil

There must be something you like among that lot. Try them as first inversions to spread the harmony out and just stab at them over a rhythmic G bass. Try solo lines from the component notes. You could be the first on your street to go modal.

FROM AUTOMATON BY HOWARD JONES

Not much to say about this one other than it shows what happens if you invert four-part chords. Strictly, as A flat is the bass, the chord should be described as A flat 6/9 (-5) but as there's not a third or seventh in sight it's a rather moot point. Much easier to leave it as B flat (A flat bass). The chord is effectively used after a 'straight' A flat major and appears in the chorus of 'Automaton' by Howard Jones.