Watch the 3 Ways To Think About Modes online guitar lesson by Jon Finn from Modal Rock Soloing
One of the distinctions I want to make is the difference between a mode and a modal fingering. When the music, the melodies and chords center around one strongest note, that note is said to be the tonal center. When the tonal center is the 1st degree of a major scale (think "doe, a deer, a female deer"), then the mode is said to be Ionian. More commonly, it's just called the major scale.
If you take that same group of notes and phrase them in a way where the 6th degree (or "La") of that same scale seems to be strongest, then you're playing a minor scale (or relative minor). In these two examples, you could use the same fingering. What makes the difference is which notes are emphasized in the musical phrases.
Therefore, one fingering of a major scale can produce any mode based on a major scale.
Conversely, playing the correct modal fingerings does not NECESSARILY mean you're playing in a certain mode:
A MODE is when the tonal center (strongest note) of the meldody and chord progression comes from a major scale, but does NOT center on the 1st degree.
A MODAL FINGERING is when the scale comes from a major scale, but the lowest note of the fingering is not the 1st degree.
Because a lot of modern rock chord progressions are based on modes, it's important to understand their tendencies.
Let's start with these three definitions:
1) A MODE is a major scale starting and ending on any other degree other than the first.
Ex: A Dorian in a G major scale starting from it's 2nd degree
2) A MODE is a major scale with notes altered.
Ex: A Dorian is an A major scale with lowered 3rd and 7th degrees.
3) A MODE is a pentatonic scale with notes added.
Ex. A Dorian is an A minor pentatonic with the 2nd and 6th degrees added.
All three definitions are important because each gives a unique perspective. Your home looks different from the inside than it does from outside. Further, the back looks different from the front. But your mind accepts all of those perspectives as "your home" if you catch my drift. So it is with modes. Learning modes from all three points of view gives you a far deeper understanding.
This next set of modal fingerings all start from G, but are related to different keys. Further, the fingerings are simplified to one octave. This is done so that the fingerings are easy to learn. For now, focaus on how they're related, but also on how they're different in tone and character.