Salut Andrew,
Are there any rules, beside creativity, that alow us to shift/modulate between, for instance, E Major and E minor scale, and then any other key? I know that the scale will sound accordingly to the context but it seems there is a specific step to make in general (and in Wallimann's lesson).

About terminology: Modulation and Landing Notes, what are they exactly?

The spoken introduction and text Wallimann did was something new and important but some more written information about this concepts, as you did with TGV country picking would be very welcomed.
I've been picking lots of information but some lessons could help me to ground!
Merci

Link:http://www2.guitarmasterclass.net/solo-guitar/slow-pentatonics-lesson/

There are no hard and fast rules to thiss, but here are a couple of pointers:

1. Modulate between keys that share a lot of notes - for instance Relative Minors/Majors share the same notes so work well (e.g. C major to A minor), relative modes as well (e.g. C major to D Dorian). Your example E minor to E major is a tough one because there are 3 different notes between major and minor of the same key, but they at least share the same root note which helps a lot.

2. Use the circle of 5ths to find closely related keys - keys next to each other on the circle fiffer by one note so are alo good candidates for modulation.

There are theory lessons on both of these conscepts on my lesson board.

And a word on landing notes - a landing note can be regarded as the first note in the new key when you modulate. There are 2 things you need to do with a landing note in order of importance:

1. Make sure the landing note is in the new key not the old one
2. Make it a strong note in the new key, such as a root or 5th - this will help to add conviction to the change.

Thats about it for now, but you are right, this would be a good subject for a lesson

The chord's notes have to be the same as the scale you're using.
Hence, chords with few notes, for example powerchords, makes you able to use Lots and lots of different scales.

Example:
Emaj+F#m7 chords
On Emaj you can use Lydian, mixolydian and ionian. But let's say you go Emaj7 too, then you can only use E lydian and E ionian, because mixo has a dominant 7th (maj 3 and minor 7 compared to ionian.)
Then, when you go F#m7, you can for example use aeolian, phrygian and dorian.

Another thing that I want to make clear, is that even if you stick to Ionian through the whole solo, it will sound dorian when the IIm7 chord is playing. this is because the chord's in dorian's position. This isn't really modulating, although you are indeed using modes.

Let's make it clearer. The chord's characteristic (minor, major, maj7, min7, diminished, etc) and its position (I-VII) is what makes your scales sound of different flavors.

Again I emphasize that even if you Play E Ionian, you will still sound Phrygian if you Keep playing E Ionian scale over a Gm7 chord, and lydian over an Amaj7, and mixo over a Bdominant7 (B7) chord.

Hope this helps!

Edit:

You should really check andrew's lesson on modal chord progressions, it really REALLY helped me!

And sorry for spamming your forum Andrew, I just love talking about modes

Funny you should ask this, as I had the same question last night when working that Slow Pentatonics lesson as well of David's and even posted a question to David(No response yet) asking the same general thing:

http://www.guitarmasterclass.net/guitar_fo...showtopic=18341

I wanted to know why Emin scale worked in this piece and his reason for choosing it when going to Cmaj. Before I asked the question, I came to Andrew's Theory guide looking for info on modulation but couldn't find anything.

I guess I am looking for a more general understanding of what root note scales work with what keys(Or degrees of a key) other than the obvious Root or Relative minor.

The answer to this is that there is no modulation going on here. If ytou start in the key of E minor, the notes of Cmaj7 are all in that key so it all still fits if you play the scale of E minor over it. Check out my Chords for Scales lesson to see how we match the two things together!