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I'm training a music that is most on the G Major scale.. But then there's a B chord. As B is not on the G Major scale, how can I refer to it when I'm writing the chord progression?


My guess is that I should just write a III instead of a iii that would be the normal case. But what about when I must refer to an F? G Maior scale only has a F#m7/5-, how can I refer to an F?

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What do you mean "B is not on the G Major scale"? G major scale goes G, A, B, C, D, E, F#. I definitely see a B there! –  Mr. Boy Nov 28 '14 at 10:20

2 Answers 2

A B chord in G major would most likely be the dominant of the relative minor, Em, and therefore written V/vi. Is the B chord followed by an Em chord? Or even a C chord, for a deceptive progression?

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When writing down progressions in the roman numeral system, most of the time you'll simply be writing the chord relative to the tonal center.

Thus, in the examples you mention, a B chord would be III and an F chord will be a bVII. In the first case, you are altering the modality of a chord that is already in key (Bm to B). In the second instance, you're flattening the seventh-degree chord (F#) and playing it as a major (as in G mixolydian).

When substituting chords in this way, you will either be temporarily stepping out of key or the harmonic context may be modal-based instead of pure diatonic, so be prepared to alter the scale accordingly for single-note passages.

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