Briggfoot

I think you've been lead into unnecessary complications by classical musicians.

A mode is a scale, ie a pattern of whole and half steps. Nothing more, nothing less. Just as with the major and minor scales, the pattern can start on any note.

Where people get confused is that the underlying patterns are based on the diatonic rather than the chromatic pattern of whole and half steps - think the white notes on the piano keyboard. And each mode has a pattern based on the pattern you would get if you started your scale at a different point on the keyboard.

What we call the major scale (ionian mode) has the pattern whole, whole, half, whole, whole, whole, half. If you start it on C, you only play the white notes on the keyboard and get a C major scale. If you want to start on D, you have to use the black keys at C# and F# to preserve the pattern and you get a D major scale. But no matter what note you start on, any sequence of eight notes with that pattern is a major scale, and it takes its name from its key tone - ie the note it starts/ends on.

The minor scale (aka aeolian mode), has the pattern whole, half, whole, whole, half, whole, whole. If you start it on A (A minor), you only play the white notes (just like C major). If you start on E (E minor), you need to add an F# to preserve the pattern. But again, any sequence of notes with that pattern is a minor scale (I'm refering here to the natural minor scale, caused by harmonic and melodic minors are variations that delight classical musicians and are generally ignored by us folkies), and it takes its name from the note it starts/ends on.

The mixolydian mode has the pattern whole, whole, half, whole, whole, half, whole. If you start it on G you only need to play the white keys (ie no F#, just like C major) and you have a G mixolydian scale. If you start it on D, you only need the F# to perserve the pattern and you have a D mixolydian scale. Again the D refers to the key tone and the scale name defines the pattern.

The dorian mode has the pattern whole, half, whole, whole, whole, half, whole. If you start it on D you only need to play the white keys and you have a D mixolydian scale. If you start it on E you have to play F# and C# to preserve the pattern, and you have an E dorian scale. Again the E refers to the key tone and the scale name defines the pattern.

Where the classicists muddy the waters is they keep referring back to the underlying major scale. Using just the white keys, the major scale/ionian mode starts on C - the first degree of the scale, the minor scale/ionian mode starts on A - the sixth degree of the scale, the mixolydian starts on G, the fifth note of the scale, and the ionian starts on D - the second degree. Thus the white note scale built on A is the minor/ionian of C, the one built on G is the mixolydian of C and the one on D is the dorian of C. Using that terminology a D mixolydian scale can also be referred to as the mixolydian OF G -- it shares a key signature with G major (one sharp) and starts on the fifth degree of the G major scale. The thing to look for is that sneaky word "of". Folk usage tends to ditch it and just refer to the scales by their keytone and pattern, ie D mixolydian.

I hope this helps and good luck with your explorations!