J'ai trouvé ça, un truc assez construit, mais je me demande si le gars n'a pas un peu tendance à confondre "triton" et "mode locrien"!!
Citation:
Here is the last mode of the major scale (we have already discussed the Aeolian mode in the topic on minor scales): the Locrian mode.
A weird mode... very dark... very dissonant: not only does it have a b2, but it also exhibits a b5!! The most important interval in the scale (between the tonic and the fifth degree) is an unstable tritone!!!
There are very few examples of classical compositions based on the Locrian mode. In fact, this mode did not even exist in the Middle-Ages; it was added much later on by theorists for consistency. Anyone composing in and playing the Locrian mode in the Middle Ages would have been tied straight onto the woodshed and burnt for satanic wizardry and black magic! Musica diabolica!
...no wonder it's been used so heavily by lots of metal groups, including Slayer, Sepultura and Napalm Death... if you see what I mean!
The Locrian mode is best used with a drone. Dissonance suits this mode very well!
Usage
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A. Harmonisation
Compared to the major scale (W W H W W W H), the pattern of the Locrian mode is:
H W W H W W W
or, in terms of intervals wrt the tonic
1 b2 b3 4 b5 b6 b7 8
Its discriminant note is the b5.
We can harmonise this mode, as we did for the major scale; this gives the following chord system:
im7(b5) bIImaj7 biii7 iv7 bVmaj7 bVI7 bvii7
Example:
Harmo of the C major scale: Cmaj7 Dm7 Em7 Fmaj7 G7 Am7 Bm7(b5)
Harmo of the C Locrian scale: Cm7(b5) Dbmaj7 Ebm7 Fm7 Gbmaj7 Ab7 Bbm7
The chords for C Locrian are in fact the same as those for Db major, but shifted.
The tonic chord is of course i7(b5).
The discriminant chords are by definition those containing the discriminant note; they are the chords build on the 1st, 3rd and 5th degrees. ALL these chords will be used extensively, INCLUDING the semi-diminished m7(b5) tonic chord!! In this respect the Locrian mode is different from all the other modes.
B. TYpical cadences
The cadences most often found in Locrian are:
i7(b5) - - - / V5 - - -
i7(b5) - - - / biii7 - - -
i(b5) - - - / bII5 - - - / bV5
As always, you should avoid the cadences that sound major.
Homework
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Other than the names mentioned above, other guitarists have spiced up their playing with touches of Locrian sound (even if they have not really composed in this mode). Listen to "Purple Haze" and "Crushing Day" for example.
