Tonal groups

Hi.

As a teacher, next week I have to explain tonal groups in major and minor tonality.
I would like to have your opinion about it.

MAJOR TONALITY

The pentatonic scale gives *modal* harmonic and melodic material. There is no tonality in pentatonic music.

Tonality comes from the introduction of two halfsteps which extend pentatonic in two different direction: harmonic (above C = B) and subharmonic (under C = F). These are tension notes and the subharmonic one (F) gives much more tension than the harmonic (B).

Tonal groups in major tonality are so defined:

Tonic: chords without tension notes or with the less tense (B), I VI III
Subdominant: chords with more tension (F), IV II
Dominant: chords with both tension notes (tritone), VII V

From this explanation, the dominant triad would not be in the dominant group and actually, without the dominant seventh, the V-I progression could be considered as a I-IV.

MINOR TONALITY

In my experience it does'nt exist a natural minor *tonality* while exist an eolian modal context.
A minor tonality derives from the introduction of G# in eolian mode. This note gives a lot of tension more than the previous two (B and F) since it appears beyond a chain of seven perfect fifths which is the normal diatonic area. For this reason G# is used mainly in chords which stay in a diatonic context, E7 and G#°, while chromatic chords (as defined in my previous post) are less used: AmM7, Cmaj/#5.
Tonal groups in minor tonality are:

Tonic: chords without tension notes or with the less tense (B), I III
Subdominant: chords with more tension (F), IV VI
Dominant: chords with maximum tension (G#), V VII

Bm7/5b is a special chord since it contains a lot of tension (tritone) which resolve on 3 and 5 of the tonic but without G# which would resolve on 1. So I feel this chord stay between dominant and subdominant group.

BOTH

In both major and minor tonality (C and Am) five chords remain in the same group:

Tonic:Cmaj7 Am7
Subdominant:Fmaj7 Dm7
Dominant:G7 (G#°7)

Two chords change tonal group:

Bm7/5b loose some tension and pass from dominant to subdominant/dominant
Em7 pass from tonic to dominant (E7).

Also I don't know nothing about traditional harmony regarding tonal groups in minor tonality and I would like to have some information about it.

Ciao

Lorenzo