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Tip: More on the dom7b9

Hello, again. We’re back looking at the “Dangerous” dominant 7, flat 9. This is a chord you see a lot of before going to a minor key, and that’s one of the reasons it sounds dangerous when we hear it. The flat 9 of the dom 7 b9 chord turns into the b6 of the tonic chord we expect to come next. A tonic chord is the central, most important chord of a key center, whether major or minor. Major key centers, most times, do not use scales with flat or minor 6s, preferring the major 6s instead. For example, note A in C major is a major 6 up from C. But minor key centers commonly DO use scales that DO have minor 6s in them, such as A harmonic minor or A natural minor.

Whew! That’s a roundabout way of explaining why we anticipate a minor key center when we hear that flat 9 in a dominant 7 chord, such as the F note in E7b9. And a side note but an important one, as I look at this bunch of text used to try to explain the dom 7b9. If you don’t understand the stuff written here or in the last issue, do not despair. Your musical ear know perfectly well what’s going on; and words often get in the way of trying to explain these so called theory topics. Keep playing and asking questions like “Okay, the F note over the E7 chord makes the E7 sound dangerous. Why? Let me track that F into the next chord and see where it fits in the next chord or key center.” Persist, and you will get it.

Okay, enough pep talk. Let’s look at one more reason why the dom 7 flat 9, such as the E7 b9, sounds dangerous. Yes, that F note is telling us “something wicked this way comes,” in the form of an A minor key center. But that’s not the only reason that F sounds dangerous. Think about what the F note is to the root of the E7 chord: yes, it’s a flat nine. That’s dissonant. Check it out by playing the E note on string 4 and the F note on string 1. In comparison, play that E note with the G# on string 1 (fret 4). Much sweeter, isn’t it?

We did that little exercise to show that dom 7 b9 chords sound dangerous partly because the flat 9 is claustrophobically close to the root of the chord.

Thanks for reading.

Copyright © 2008 Darrin Koltow

This first appeared in the Guitar Noise News – July 1, 2006 newsletter. Reprinted with permission.

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