Lesson no. 5
Seventh chords
OK, so we have been discussing the method of determining chord structure by the counting of intervals. We have learned to make major chords by making triads of the first note, plus the third and fifth interval notes according to which notes are sharp (or flat) in which key. To determine that, we count the intervals by the method:
whole step-whole step-half-step;
whole-step whole-step whole-step half-step.
And we have learned most particularly to remember to always count those intervals, not just the note name. So what is the difference ('cause you know there's a loop being thrown soon!) between that and the sevenths? Well. while a major chord is composed of a triad, or three note combination, so is the minor chord (which we'll tackle next week). But the seventh chords have to have FOUR notes.
The seventh chord form of the major (not minor, like I said we'll discuss that next lesson) uses the triad of the major chord plus one more note. And, as you can guess, it is the seventh interval. If you'll check the last lesson ("archive lesson 4") you'll see a listing of the major chord triads for each key. If you count the intervals one, three and five you'll have the major chord. If you add the SEVENTH interval, you'll have the seventh chord, right? (Here it comes!!!)
WRONG! You need the flatted seventh interval to make the seventh chord. But if you use the seventh interval you will have the MAJOR SEVENTH chord, which is a different chord from the SEVENTH. In other words, C7 is different from Cmaj7, in that C7 has the flatted seventh interval and Cmaj7 has the seventh interval. Or:
C7 is: C - E - G - B flat; while
Cmaj7 is: C - E - G - B
Why is this? Well, my impulse is to say, "No one knows, it's one of those mysteries of life that mankind was never meant to understand." But of course that's not the case. There is a perfectly valid reason for it, but darned if I can remember what it is. It's been years since I studied my music theory, and if you want to enlighten me (or complain that I am an idiot) please do so. Consider it an "extra credit" question, if you wish, although what you'll get out of it except personal satisfaction I don't know. The point I'm making here is that this course of study in theory for guitar is a totally pragmatic, practical set of lessons, and I'm just not going to get bogged down in all the details of music theory. It's a fascinating subject, and can easily occupy all your time, and mine. I've got too many other things to do, though, and I suspect you do, too!
Anyway, that's it for this week. Tune in next time, when we will learn to make MINOR chords and the MINOR SEVENTHS.