I was transcribing a jpop song when I came across this chord progression:

Bb | C Bb | Am | F#dim |

C# | C# | C | C |

F#m7b5 | B | E | .....


I think the song changes from D major to D minor in this part, starting from the the first Bb chord. It then changes to E major after the last B chord.

I'm confused about the usage of C#, C and F#m7b5 in the progression. They don't seem to be in the key of Dmaj, Dmin nor Emaj. Furthermore, While the F#m7b5-B-E progression is similar to a II-V-I cadence, I don't understand why the fifth of F#m7b5 has to be flat.

  • what's the song? I'm really interested to hear this snippet in context, proper interesting harmony here! – Some_Guy Apr 12 '17 at 12:54
  • The song is Star!! from a Japanese show called Idolmaster, this snippet is taken from 0:48 of the song. – James Apr 13 '17 at 9:51

The piece definitely begins in D major, then progresses down by consecutive major seconds to reach that B♭ chord to give it a sense of D minor (the Am chord also helps with this).

The second line of your chords, with the C♯ and C, are suggested to me F major (the relative major of D minor). Thus the C♯ chords might better be spelled as D♭, and this system is just a ♭VI--V progression in F. This F never appears, but imagine that last C chord resolving to F, and you'll hear that F major is definitely implied.

That C chord just resolves deceptively to the F♯m7♭5, which is then treated as a ii half-diminished seventh in the key of E, and the final three chords are just a ii--V--I to cadence in E. Normally in the key of E this ii chord would just be F♯m7, but the composer added in a bit of chromaticism and "borrowed" the F♯ chord from E minor, which has a ♭5. We call this "mode mixture," and it's a very common and effective tool.

  • 1
    Great analysis. Just wanted to tack on some "feelingy" stuff to the end of it; the "effect" of using the Fø B7 preps us to hear E minor, so that when the E major comes instead, it sounds very bright; like a picardy third thing. So when OP says "why does the 5 have to be flat", in terms of how the music feels, it means that it makes the E major chord really "pop" in a sense, giving it a kind of "strident" or "bright" sound to it. – Some_Guy Apr 12 '17 at 13:24

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