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In the last few lessons, Brian often refers to tricks and ways to embellish chords by means of higher extensions.
Let’s have a look at the theory behind that.General aspects
In any chord, the root, the third, the fifth and the seventh are the chord tones (the third and the seventh may be minor of course, and the fifth may be diminished).
Everything else is a potential tension (particularly the 9, 11 and 13) that you can add while playing rhythm or lead, provided it doesn’t clash with the melody.
Adding those other notes will inevitably create dissonances, and we have two somewhat conflicting requirements:
1) the tension should last at least one beat, otherwise it will just be a passing note and it won’t count as a tension
2) the tension should remain “musical” so we will need a criterion to decide what is musical and what is not, that is to say what notes we keep (the available tensions) and what notes we avoid (the avoid notes)When you add tensions, the chords quickly become difficult or even impossible to play on a guitar, so you will have to ditch notes. In most cases, you’ll want to keep the third and the seventh of the chord (the guide tones) because they define the chord. The root and the fifth are less important.
It is important to understand that tension notes are added to the chord and don’t replace chord tones. For example, (D, F#, A, C, E) is a D9, but (D, E, A, C) is a D7sus2.
Tensions on non-dominant chords.
– First write down all the chord tones
– All the notes a semitone above the chord tones are avoid notes
– All the notes two semitones above the chord tones are available tensions
– All the remaining notes are avoid notesFor example, let’s take Em7
– the chords tones are E, G, B, D
– the avoid notes are F, G#, C, D#
– the available tensions are F#, A, C# (9, 11, 13)
– A# is an avoid noteOther example: Amaj7
– the chord tones are A, C#, E, G#
– the avoid notes are A#, D, and F
– the available tensions are B, D# and F# (9, #11, 13)
– C and G are avoid notesBut we also need to look at the function of the chord or, equivalently, at the key. If the Em7 chord is the iii chord (we are obviously in C Major), the notes F# and C# don’t belong to the key. So if we want to play “in”, we better avoid these two notes.
On the other hand if that Em7 is the vi chord (we are in G Major), only the C# is questionable.
In D Major Em7 is the ii chord and there is no problem at all.Tensions on dominant chords.
Those are a bit different because they already contain a strong dissonance (the tritone), which is inherent to that chord type. That tritone sits between the third and the (flat) seventh of the chord, in other words between the guide tones. So, in order to preserve the quality of the dominant 7th chord we usually avoid clashing with those tones.
– Write down the chord tones
– the guide tones (3 and 7) plus one semitone are avoid notes
– all other notes are available tensionsFor example: C7
– C, E, G, Bb
– F, B are avoid notes
– everything else is an available tensionHave fun with all those dissonant jazz tones!
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