Every time I play major7th or minor7th it doesn't make me feel any different than the normal major or minor chord, so what's the point of such chords? What do these chord qualities accomplish that simpler chords do not? Is there a real difference?
7th and suspended chords are often used to explain away melody notes as chord tones instead of labelling them as nonchord tones. (Accented nonchord tones sometimes make less sense than just plain calling them chord tones.)
Dominant 7th chords (or major chords with an additional minor 7th from the root) are also used to unambiguously prepare tonicizations or modulations. For example, while spamming C major chords can make you think the piece will remain in C major, adding a single C7 chord will often make you think an F major chord will come next (as, in C major, C7 is V7/IV).
Jazz often uses 7th chords because that is somehow the convention, though. Yes, this includes using a 7th chord for the tonic. Anyone can explain this convention?
I've heard some more modern pieces that use several parallel sus chords in a row (mainly video game themes, the occasional contemporary piano piece), probably because they sound cool and suggest quartal harmony (a sus chord is an inversion of a quartal chord consisting of two stacked 4ths).
it doesn't make me feel any difference than the normal major or minor chord, so what's the point of such chords?
One tricky thing about music is that it's subjective, and different people feel different things! Personally I feel that a minor seventh is much deeper and more mysterious than a straight minor chord, and I find that sus2 (or 5 add 9) chords have a real emotional multidimensionality to them. That's just me of course!
Of course there might be lots of aspects in harmony that you enjoy that I don't appreciate. A lot of things that are supposed to "make sense" in common practice harmony leave me cold, or even slightly nauseous.
When you’re first learning about music, seventh chords can sometimes seem like an unnecessary adornment. I remember thinking about them the same way you do. I greatly preferred regular major and minor triads because they sounded better—consonant is the technical term—and indeed they are. Like coffee or olives or blue cheese, seventh chords may represent an acquired taste. You have to get used to hearing them in context with a harmony to appreciate what they do.
There is a dissonance within seventh chords which makes your ear want to hear a resolution. Take a G7 chord as an example. The constituent notes are G B D F. The B and F together form a tritone. It’s the interval between a perfect 4th and a perfect 5th. Try playing just B and F together and you’ll see that they don’t sound consonant at all. Throw in the D as well and you’ve got a diminished chord.
Both diminished chords and dominant seventh chords often serve the same function: to prepare your ear to expect the tonic chord. In the case of G7 or B°, that is C (or Cm if it’s in the minor key).
Suspensions have a similar effect. They want to resolve to the major or minor triad. The major second interval within every suspended chord is less consonant than a major or minor third. (In a sus2 chord, the major 2nd is between the root and the second. In a sus4 chord, it’s between the 4th and the 5th.) So Dsus2 or Dsus4 chords would resolve to D or Dm, for example. It’s rare that it doesn’t happen.
So whether you hear it or not—and if you spend enough time, you eventually will—the point of seventh and suspended chords—at a basic level—is to create tension to be released.
Maj and min 7th chords, and even more suspended chords, do sound different than major and minor chords - just not so much because there's either an extra, or a different note in the chord - all the other notes are the same.
One reason I use these chords when writing songs is variety, having more options. If a chord progression is in the key of C major, I sometimes play the C as a C maj 7th, the A as an A min 7th the G as G7th so on and so forth.
Sometimes I choose one of them, at others just a normal major or minor. I see what's best for that particular song. There's a lot of subjectivity here.
- On a more objective side 7ths and suspended chords tend to cause tension in music - dissonance.
And something our ear really loves hearing is dissonance being resolved into consonance.
This is especially the case with suspended chords. Play a D sus for followed by either D major or minor.
Can you hearthe dissonant note being resolved?
The point is to create tension and then relaxation. That is how music moves you.
Suspended chords (sus) want to resolve towards the third. The seventh chords (and chord tensions such as the 9ths, 11ths, 13ths, and 6ths) all create and resolve tension to various degrees.
If you grew up watching Warner Bros cartoons, you would immediately recognize the frequent dim7 sliding in minor third intervals during the climactic scenes of the Road Runner & Coyote cartoons.
Create the tension, then release it. That is the essence of musical communication. These additional chord voices provide more vocabulary for the musical language.