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16. Prelude and Fugue in G minor from Book 1



                    Try speaking this in the rhythm of the opening of the Fugue subject!

When we moved, for any number of sensible practical reasons, from a romantic Tudor cottage to a suburban town house, the one consolation to my sense that this was a regressive step was the house number. 49 is a special number because it is a square number. Not just any square number, but the square of one of the most magical, mysterious and mystical of all the numbers, the number 7. The seventh movement of Messiaen’s Quatuor pour le fin du Temps depicts rainbows - with their traditional seven colours - for the angel that announces the end of time. In the last book of the Bible, the book of Revelation, at the beginning of John’s vision on the isle of Patmos we read : I turned round to see who had spoken to me and when I turned I saw seven golden lamp stands and at the centre a figure like a Son of Man….In his right hand he was holding seven stars. The most common musical scales have seven different notes. There are seven different letter names in music which countless generations of music students have remembered in the order FCGDAEB maybe using a mnemonic such as Father Christmas Gave Dad An Electric Blanket. This gives the order of the keys in the circle of fifths and also the order of sharps as they appear in key signatures. If, for instance, you see a key signature with three sharps those sharps will be F,C and G. If you see a key signature with six sharps they will be F,C,G,D,A and E. The beauty of this sequence is that the reverse works for the flat key signatures. So even if you never learnt a reverse mnemonic (such as Blanket Exploded And Dad Got Cold Feet) you can generate the order of flats simply by reversing the order of letters. Thus, for instance, if you see a key signature with three flats they will be B, E and A. If you see a key signature with six flats they will be B, E, A, D, G and C. In other words this simple sequence of seven letters can reveal the whole structure of the circle of fifths, the fundamental building block of the key relationships in Western music from the Baroque period onwards. Another fascinating musical journey involving the number 7 lies in exploring the different types of seventh chords. Most theory books will give you charts of five sets of seventh chords to learn; that is five for each of the twelve chromatic notes, i.e. a total of sixty different chords. This can be rather daunting until you really understand the patterns involved. The ‘simple’ seventh chord, the one notated as C7, G7 etc. , is in a way not that simple at all. It always contains one note, the seventh, which is NOT present in the root scale. So a C7 chord includes a B flat, not a B natural. I always explain this by way of linking the C7 chord to the key of F. The scale of F of course DOES include a B flat, and so understanding the C7 chord belonging there makes perfect sense. My experience is that once people really understand this, it is quite easy to develop a theoretical understanding of the whole circle of fifths: C7 belongs to F F7 belongs to B flat B flat 7 belongs to E flat E flat 7 belongs to A flat A flat 7 belongs to D flat D flat 7 belongs to G flat G flat 7 (= F sharp 7) belongs to B B7 belongs to E E7 belongs to A A7 belongs to D D7 belongs to G G7 belongs to C Of course to have a real practical knowledge of this at the piano means spending time learning the physical connections between the adjacent keys and chords. This work will prove to be of enormous benefit with playing not only classical repertoire but also playing jazz standards from lead sheets. The minor seventh chord, notated Cm7, Gm7 etc. , is puzzling to many students in the early days because the difference between C7 and Cm7 is nothing to do with the seventh of the chord at all but to do with the third. C7 has a MAJOR third, Cm7 has a MINOR third. How confusing is that? No wonder many people despair of the wonders of music theory! The major seventh chord is the one which DOES include the seventh note which is present in the root scale. Thus C maj7 includes a B natural; G maj7 includes an F sharp. Another way of thinking about the major seventh chord is that it combines the sound of the major and the minor triads. Thus a C maj7 chord can be heard by playing a C major triad and an E minor triad simultaneously. And whereas the C and B sounding together are jarring to most peoples’ ears, once you place the E and G in the middle the sound is quite mellow. The half diminished seventh is another common jazz chord and it is particularly useful in a minor key where it is the key built on the second degree of the scale. This can be understood as a minor seventh chord with a flattened fifth and indeed can be annotated as for instance Bm7(b5), the chord on the second degree of the A minor scale. The diminished seventh chord is built out of a series of minor thirds; all the distances between the notes of the chord are equal. This chord, much loved by silent movie pianists, creates a dramatic sense of tension more easily than anything else in music. It was also used to great effect by Bach (e.g. with the choir shouting Barabbam in the St Matthew Passion) and Beethoven (e.g. the transition into the finale of the Appassionata Piano Sonata, Op 57). So why stop at five seventh chords? Why not seven? The chords C-E flat - G -B natural and C - E flat - G flat - B natural are also seventh chords. I think it is time to proclaim the full seven - seven system of chords. A suitable creative venture to come from house number forty-nine!!