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hpr1754 :: D7? Why Seven?

I explain what 7th chords are and when to use them.

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Hosted by Jon Kulp on 2015-04-23 is flagged as Clean and is released under a CC-BY-SA license.
chords, music theory, music, harmony. 5.
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Duration: 00:13:52


In this episode I respond to one of the community-requested topics ("Music Theory") and try to explain what seventh chords are and why they are used. Below are some of the terms that I use in the course of the discussion.

  • Interval: The distance between two pitches (sounded either consecutively or simultaneously)
  • Consonance: Relatively stable sound between two or more pitches
  • Dissonance: Relatively unstable sound between two or more pitches. Dissonance often needs a "resolution" to consonance
  • Chord: three or more notes sounded together
  • Chord progression: a succession of chords
  • Triad: a chord with 3 pitches, the adjacent pitches separated by the interval of the 3rd.
  • Seventh chord: a chord with 4 pitches, the adjacent pitches separated by the interval of the 3rd.
  • Tonality: harmonic system that governs the use of major and minor keys
  • Tonic: the central tone of a piece of music
  • Mode: major or minor [e.g. Symphony no. 5 in C minor]
  • Modulation: the process of changing keys within a piece of music
  • Scale: Ascending or descending series of notes that define a key or tonality, with a specific arrangements of half-steps and whole-steps. Major and Minor scales are most common in Western music

Free public-domain music reference book: Music Notation and Terminology by Karl Wilson Gehrkens: (see ch. 18)

Free Online Music Dictionary:


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Comment #1 posted on 2015-04-10 19:56:42 by FiftyOneFifty


I thought this was going to be a podcast on Klingon battle cruisers.

Comment #2 posted on 2015-04-23 02:27:06 by Jon Kulp


Sorry Fifty, I don't even know what those are! Maybe you can record a follow-up. I actually thought the title might be confused with Star Wars droids, the Klingons never occurred to me.

Comment #3 posted on 2015-04-29 05:26:51 by thelovebug


I found this incredibly interesting as a musician with virtually no formal training... I look forward to hearing more on the theory of chord progressions!

Thanks Jon!

Next: Major 7ths? Probably my favourite chord to (over)use.

Comment #4 posted on 2015-05-10 00:13:00 by FiftyOneFifty

Explaining myself

The Klingon ship from the original Star Trek series was a class D7 battle cruiser and you can still see the model still in use in the later series (Next Gen, DS9, Voyager).

Comment #5 posted on 2015-05-10 10:47:49 by Jon Kulp

I kinda see the resemblance...

That ship actually looks like it has some dissonance in it, such as the tritone between the C and the F♯ that I mentioned in the d7 chord the

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