Help me understand this progresion: F, B7, Bb7, Eb7

Discussion in 'Playing and Technique' started by Jamar, Jan 19, 2015.

  1. Jamar

    Jamar Supporting Member

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    I was messing around tonight and stumbled upon this 4 chord progression that cycles nicely. I played these four chords only using three notes max:

    F = F, A, C
    B7 = B, A, D#
    Bb7 = Bb, D, A
    Eb7 = Eb, G, Db

    The progression has a great chromatic tritone decent thats makes its real fun to solo over. I was able to use a mix of F major pentatonic and added chord tones with a lot of success.

    I don't understand what key the progression is in. Will someone help enlighten me?
     
  2. stevel

    stevel Member

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    If you hear F as the tonic chord (likely since it both begins the cycle and is just a triad) we would say the key is F Major.

    Just because any chord progression contains chords that are not in the key does not mean it's not in any key. When a key is established, as long as there aren't so many chords that disrupt the key center, we'd still say it's in the original key.

    That said, popular music of the 20th and 21st centuries have stretched the boundaries of what it means to be "in a key" in a way that the original definitions of "key" weren't designed to explain (they didn't need to at the time).

    But even in the past, it was commonplace to borrow chords from the parallel mode and include other non-diatonic chords, usually either from a modal influence, or a secondary key. However, secondary key chords were generally resolved back in the key.

    Flash forward to the 20th century and more and more chords from modal origins became accepted, more chromatic medians and "color" chords, and secondary chords without resolution. Planing and parallelism allowed chord progressions that were otherwise non-diatonic to make perfect sense when they followed a chromatic descent, or other more linear idea (half-step resolutions, and so on).

    F is from the key of F.

    B7 is not.

    However, it is a Tritone Substitute for F7.

    It's common to go from I to V7/IV, which is I - I7 if you like - F to F7.

    F7 goes to Bb, the IV chord, so the following progression is commonplace:

    F - F7 - Bb

    All you've done is used a tritone sub (B7) to replace the F7.

    It's also not uncommon for any chord to have a 7th chord that leads to it.

    Eb7 is not really in the major mode of F, but it is in the parallel minor.

    At any rate, Bb7 resolve to Eb. It's also not uncommon to have a string of 7th chords that resolve to each chord in the key, but that chord itself turns into a 7th chord to push onward to the next chord, which becomes a 7th, etc.

    F - E7 - A7 - D7 - G7 - C7 - F

    F - E7 to Am (A7 to Dm) D7 to Gm (G7 to C ) C7 to F.

    Bb7 goes to Eb - usually you don't do this because it's not in the Major mode of the key, but with blues influences, the b7 is common enough.

    And the blue influence is another reason for a IV7.

    Honestly though, your progression is a bit "abrupt". What makes it "work" is that we're so used to hearing 4 chord cycles where the I starts each pass, and we're so accustomed (for centuries) of accepting repeated patterns that start on I as nothing crazy when the phrase ends in an odd key or chord, and then "jumps" back to I.

    This has kind of a Beatles-esqu feel to it to me.

    But do this:

    F - B7 - Bb7 - Eb7 - Ab7 - Db7 - C7 - F

    That Db7 - C7 - should sound like a very typical blues ending.

    Now, that's not to say you have to *treat* the whole thing as it's in F Major. It's also commonplace (especially in blues) to treat something like the IV7 as a new key for *soloing* over. But again, as long as the primary key center is not disrupted too badly, it stays in that key.

    Best,
    Steve
     
  3. Jamar

    Jamar Supporting Member

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    Wow. Thanks for the thorough response, Stevel. You given me a lot to digest. I'll take another look at this tomorrow with guitar in hand. Thanks again!
     
  4. JonR

    JonR Member

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    Also worth pointing out that the Eb7 can easily resolve back to F. This is common in jazz, and is known as the "backdoor progression". If you try Eb9 > Fmaj7, I think you'll see (and hear) why it works:
    Eb9 Fmaj7
    -6----5------
    -6----5------
    -6----5------
    -5----7------
    -6----8-----
    -----------

    Notice all those half-step falls, which nicely counter the whole step rise in the bass.
    That hints that Eb9 can be seen as a sub for Bbm, the minor iv chord in F major.
    So - assuming your Eb7 does go back to F ;) - your sequence is a kind of alternative to:
    F - F7 - Bb - Bbm - F...
    - an old pop/jazz cliche, which is made somewhat cooler by your two subs! :)
     
  5. Jamar

    Jamar Supporting Member

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    Thanks JonR. After Stevel's explanation of the B7 sub for F7, your explanation of the Eb7 sub for Bbm helps answer some of my lingering confusion. I think I heard this concept once watching this Joe Pass video (around 4:50).




    I love a "I, I7, IV, iv" progression, so it makes sense that my "new" progression hits my ear pleasantly.

    I'm sure these sorts of tritone substitutions are old news to a lot of jazz guys, but they're new tools of application for me. I really love songs that have these half step falls: Dylan's Lay Lady Lay and Make You Feel My Love are two that come to mind. Also I've noticed this in a good bit of jazz:



    I've been trying to successfully integrate this concept into my songwriting for a while and I think I was able to do this for the 1st time last night without it really feeling forced.
     
    Last edited: Jan 20, 2015
  6. guitarjazz

    guitarjazz Member

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