On the guitar, the major scale has seven degrees, and technically any one of them can function as the
tonic — the tonal center, or primary pitch, of the scale. The sound and feel of the scale changes depending on which scale degree is heard as the starting point. The Greek names used to identify the seven modes of the major scale are Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian, and Locrian.
Although the major scale technically has seven modes, one of them, the seventh mode (Locrian), isn’t used.
How modal sounds are made on the guitar
Making modes is just like mixing colors. With colors, yellow and blue make green, red and blue make purple, and so on. You can’t understand what green is like by looking at yellow or blue alone. Only when the two colors are mixed is the new color, green, revealed. The same is true with music modes.
In order to produce modal sounds, you need to mix major scale patterns with the proper accompaniment. The only way you can truly hear a modal sound is by playing a major scale over music that centers on a scale pitch other than 1. You can get the necessary accompaniment by playing along with song recordings, play-along tracks, looping devices, software programs and, of course, other musicians.
How to approach modes as more than just patterns on the guitar
You don’t need to learn new scale patterns in order to play modes. The same patterns that are used to play the major scale on the fretboard also produce all the other modes when applied correctly.
You can’t create a complete modal sound by simply starting on a scale degree other than 1 or playing a particular major scale pattern. You really need to hear the scale combined with accompaniment in order to hear the true modal harmony.
When you mix the major scale with the right chord, the modal sound is produced even if you don’t start on the first modal pitch and regardless of which position or pattern you use on the neck.