If I ascend from ‘C’ Tonic 8 semi-tones, I arrive at ‘G – Mixolydian / a 5th.
If I descend from ‘C’ Tonic 8 semi-tones. I arrive at ‘ F’… Do I play the Intervals of, ‘F’ Mixolydian, or ‘F’ Lydian?… am I also at a, ‘5th.
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Hi Donn.
If you are in the key of C then you should just stay in C major and not think about modes. C “tonic” can mean a lot of things but if you are referring to key, then the related modes will never change i.e., G will always be Mixolydian and F will always be Lydian. Pitch direction doesn’t make a difference.
I reiterate___ I use Intervalic Degree and Modes, to access the Note and Tonal qualities of the Key I am in. I just want to understand, ‘Why’?,… a ‘5th’ in one direction, is a ‘4th’ in another direction. There has to be a, ‘logical mathematical explanation’. So far, No one seems to know.
The logic is simple. They are two different things. The interval is always a fifth, regardless of direction. However, the note you land on, depending on direction, will be different.
Forget all about music for a moment and answer me this.
1 2 3 4 5 6 7 8
If I count three numbers forward from starting from the left, I stop on 3. If I count three numbers starting from the right, going backwards I stop on 6. Both three steps, two different landing points.
Change the numbers above for letters and there is your answer.
C D E F G A B C
You need to stop thinking about F Lydian being in the key of C major. They are two different keys. You are going wrong because you are looking at modes incorrectly. “F” in the key of C is F in the key of C, the fourth degree, nothing else. Once you make that “F” Lydian, you are no longer in the key of C, you are in the key of F. C is no longer the root, it’s now the fourth degree of F Lydian.
