What does 'down a minor third from the major key' mean?

Going down a minor third from the major key applies to all instruments but it's easiest to show on a piano, as follows:

What does 'down a minor third from the major key' mean? 1

What does 'down a minor third from the major key' mean? 2

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What does 'down a minor third from the major key' mean? 4

What does 'down a minor third from the major key' mean? 5

What does 'down a minor third from the major key' mean? 6

What does 'down a minor third from the major key' mean? 7

What does 'down a minor third from the major key' mean? 8

What does 'down a minor third from the major key' mean? 9

What does 'down a minor third from the major key' mean? 10

What does 'down a minor third from the major key' mean? 11

What does 'down a minor third from the major key' mean? 12

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