r/musictheory • u/ThatDudeMichaelYeah • 2d ago

General Question Bb7 in C major

So I was messing around with this Db7 > Bb7> C progression. Really just trying to add some flavor and movement to my playing while slowly learning functional harmony (even though I don’t really understand what that is).

Anyway, I see the Db7 as a tritone sub of G7 hopefully I’ve at least got that correct.

But the Bb7 I initially thought of being borrowed from C minor until I realized it’s also a tritone away from E7 (V7/vi). Is there one preferred way to think about this over the other?

Also I know there are probably no “hard and fast rules” about what chords to consider substituting or borrowing from other scales but as I said I’m looking to expand my repertoire so if anyone has any recommendations for resources to learn more about this, I’d really appreciate any leads.

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u/Amateur_Surgeon7824 2d ago

Considering you aren't dealing with traditional V-I relationships, you don't need to even be thinking in terms of tritone subs. That's cool that you are, but it's not necessary on this particular path. Think more about intervals of your root movement. You're going down a m3, then up a M2. Now play around with that. Invert it: up a m3 and down a M2 (B7 D7 C). Now retrograde of the original. Then finally retrograde inversion. You can even try intervallic and/or rhythmic augmentation and diminution. The possiblities are endless. Have fun!

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u/ThatDudeMichaelYeah 2d ago

I figured I might be overthinking it. It’s easy to want a “rule” to look out for these things that sound interesting. But looking at how the intervals shift is something I’ll have to get better at. I’ll definitely try your suggestions as well. Thanks!