Where certain chords can function in a scale for example where an augmented chord would be used diatonically (biii like in harmonic minor?) or a half diminished etc

Also switching chords around diatonically, for example subbing in the iii or vi for I, ii for IV and vii for V. Is there a version of this applicable to 7th chords and what is the name of this?
I'm not quite sure what you're asking.

Do you understand how to harmonize a scale?
Only play what you hear. If you don’t hear anything, don’t play anything.
-Chick Corea
I dont really understand your question.

But Lydian and both diminished scales can be built off diminished chords, and the augmented chord goes with the whole tone scale.

Where certain chords can function in a scale for example where an augmented chord would be used diatonically (biii like in harmonic minor?) or a half diminished etc

I'm not absolutely sure about this, but I think the triad chords function roughly the same in most diatonic scales (I think?). Because chords of a scale are built by by stacking thirds relative to the scale, the degrees would be still relative to each other just like in the major scale because the leading relations remain the same. That means the chords would be functionally the same, it just has a different sound/feel because some of the leading intervals are different.

Also switching chords around diatonically, for example subbing in the iii or vi for I, ii for IV and vii for V. Is there a version of this applicable to 7th chords and what is the name of this?

I'm not sure if it's the way you wrote that question, but as I understand it you sub by implying 7th chords, so it kinda can function both as a I or iii or even I7 depending on context. I have no clue if you can sub 7th chords, if that is what you were asking. But my guess is that you can do that with 9ths and imply it thusly?
Where certain chords can function in a scale for example where an augmented chord would be used diatonically (biii like in harmonic minor?) or a half diminished etc
I don't understand the question.

Also switching chords around diatonically, for example subbing in the iii or vi for I, ii for IV and vii for V. Is there a version of this applicable to 7th chords and what is the name of this?
Those families are also applicable for seventh chords just extend the chord to it's diatonic seventh. So IV becomes IVmaj7 and ii becomes ii7 and V becomes V7 etc etc.
Si
Sorry I know it's not worded very well at all, I'm normally quite literate but find it so difficult to explain a concept I don't fully understand, drives my teacher mad .

In my first question I was asking where in a given scale (Say the Harmonic Minor or a bebop scale etc) I can sub certain chord types. For example in a basic major scale harmonized with triads I can use maj-min-min-maj-maj-min-dim. This differs for other scales. I'm assuming the chord types chosen are chosen because of the intervals in the scale, but how can I know where to sub chord types into different scales?(say harmonizing with seventh chords a scale I'm new to like phrygian dominant, how would I know the chord sequence to follow?)

My other question was in relation to substituting chords in a progression for other chords. For example in a basic I - IV - V - IV progression, I could using the information I posted originally, turn that progression into iii - ii - V - ii. What is that substituting method called in music theory? and can it be done for 4 note chords/different chord types etc?
Sorry I know it's not worded very well at all, I'm normally quite literate but find it so difficult to explain a concept I don't fully understand, drives my teacher mad .

I can relate to that

In my first question I was asking where in a given scale (Say the Harmonic Minor or a bebop scale etc) I can sub certain chord types. For example in a basic major scale harmonized with triads I can use maj-min-min-maj-maj-min-dim. This differs for other scales. I'm assuming the chord types chosen are chosen because of the intervals in the scale, but how can I know where to sub chord types into different scales?(say harmonizing with seventh chords a scale I'm new to like phrygian dominant, how would I know the chord sequence to follow?)

Yes, it's about the intervals. Do you know *why* the triads have their specific type in a specific key? Write the notes from a major scale. Write the notes from the triads and various 7ths from that scale. Look at the notes from the scale and the notes in the chords. Look at the different intervals in those chords. What do you notice? What can you tell about the relationship between the major scale notes and the chords?
How would this change things if you use a different scale?

Then, look at the triads and seventh chords. Compare the chords you can sub with. What can you say about that?

I dont mean that in a mean "I'm not going to tell you, nyah!" way, but if you'll figure it out on a piece of paper, the relationships between stuff makes a lot more sense then if it was just explained. If you need a bit more help or hints, just ask

My other question was in relation to substituting chords in a progression for other chords. For example in a basic I - IV - V - IV progression, I could using the information I posted originally, turn that progression into iii - ii - V - ii. What is that substituting method called in music theory? and can it be done for 4 note chords/different chord types etc?

er... Its called substitution?
Sorry I know it's not worded very well at all, I'm normally quite literate but find it so difficult to explain a concept I don't fully understand, drives my teacher mad .

In my first question I was asking where in a given scale (Say the Harmonic Minor or a bebop scale etc) I can sub certain chord types. For example in a basic major scale harmonized with triads I can use maj-min-min-maj-maj-min-dim. This differs for other scales. I'm assuming the chord types chosen are chosen because of the intervals in the scale, but how can I know where to sub chord types into different scales?(say harmonizing with seventh chords a scale I'm new to like phrygian dominant, how would I know the chord sequence to follow?)

My other question was in relation to substituting chords in a progression for other chords. For example in a basic I - IV - V - IV progression, I could using the information I posted originally, turn that progression into iii - ii - V - ii. What is that substituting method called in music theory? and can it be done for 4 note chords/different chord types etc?

Wow first time I see some forward thinking in a while here, left a bunch of people baffled huh?

The sub types you are using are not particular substitutions perse but more of superimpositions based on how the chord is built.

For example, like you said for that I chord Cmaj you could play the iii and the vi because Eminor and Aminor are built off the chord tones of the Cmaj.

C E G B Cmaj7
E G B D
C E G A cmaj6
A C E G

And so on for the other chords. If you notice you can accumulate most of these type of superimpositions simply by stacking the scale chordally:

C E G B D F A

And from there messing around with it. You could do that with any other scale aside from the major and minor and get the same results. another way to look at it and remember it is by stacking the modes

Dorian ii
Lydian IV
Aeolian vi
Ionian I
Phrygian iii
Mixolydian v
Locrian vii

As you can tell they go in sequence of even and odd numbers and for whatever chord you have you can easily lightly superimpose one of the adjacent chords by it.

For the augmented chords, if you ever really use them in diatonic music is over Dominant 7th chords.

If you have G7 G B D F you can substitute that chord for it's augmented chord G + and play from there. The reason it works is because of the tritone mainly and the fact that the tension is welcoming those intervals.

If you think and play this way you'll never ever ever need scales or anything boring to improvise.