Hey Friend,
Let’s wrap this up. The last triad in the key of C major is the B diminished chord (Bdim).
B diminished is already a dissonant chord, and you are not going to see it used in Rock, Blues, or Country (okay, maybe a very rare occurrence).
When we play the C major scale over a Bdim chord, yes, there will be notes that work, but that’s because they're part of the chord. Those notes are B (the major seventh interval), D (the major second) and F (the perfect fourth).
The problem with playing over a Bdim isn’t the notes - it’s the chord.
While it’s technically correct, the chord just isn’t pretty to hear in the context of most songs. It’s that flatted fifth note that throws things all out of whack.
A B minor chord uses an F# note for its 5 note (B, D, F#), so sliding down a half step to F is the killer. But F is the note from the C major scale, so Bdim ends up being the triad that occurs naturally in the key of C major.
C major 1 2 3 4 5 6 7 (8)
C D E F G A B (C)
Take a listen to the intervals over B diminished and hear for yourself.
It’s Friday, the last day before a long weekend for most of us. Go easy on the spiked egg nog today!
Peace~
Dave
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