Something is gone amiss.Eh?
How is the interval of a (major or minor) second based on a grade name? (This is the first I've ever heard of a grade name by the way. Niotice how this is not the way the names are taught to us in modern times).
D is the second grade of C. There is a second between C and D
Between C and F there is a 4th. F is 4 of Cmajor
Between F and B there is a 4th, although augmented, because B does not belong to the F scale, but a Bb is the 4th grade of the F scale.
Interval is still a 4th.
Between G# and Fb there is still a 7th. G1 A2 B3 C4 D5 E6 F7
Major minor perfect augmented are a different matter.
If you are referring to names like "supratonic" another can of worms is to be opened.
In Italian and English a melodic tradition gives names like tonic (1) supratonic (2) mediant/characteristic/modal (3)
In German, a harmonic approach is Tonic (1) (spelling?) Subdominantparallel (2) Tonicparallel/Dominantparallel (3)
Different concepts, different traditions.
To explain this in English is really hard for me. Also it is more useful when composing or analizing than it is when improvising on a standard jazz form.
I studied in the 80s, a different century. Not sure what they teach now.
Not sure that's the reason, but it is a lucky coincidence.Eh?Say what? If that's why they called a seventh a seventh, those guys were even crazier than I thought.