The tenth

Play the following notes in ascending order

CEGBD

That's the chord C major with a 7 and 9. Now play the whole chord. Now take away the fifth (G). You don't need it. Now take away the E (3) and put another E on top, as a tenth, or a third an octave higher.

Now the chord is C BDE. It sounds really sweet. The tonic is down there as a bass note and there is a succulent cluster of chord extensions on top. Now do the same with a dominant chord: C BbDE. That also sounds good, but it will be tangy instead of just sweet. Try this in all 12 keys. You can put the sixth in there too, I've discovered, but then I had to remove the ninth so the chord could breathe and not feel so cluttered.

Each chord, or each voicing of each chord, has its own expressive potential. It's not really true that minor = sad. For example, I can use a III chord in place of a I and it often sounds triumphant, even though it is based on a minor scale. I have the chord analyzed above, in Bb, lead to a Cmin79 chord with C Eb G Bb D [natural]. Far from being sad, the chord sounds rich, meaty, and satisfying in context. For some reason this chord has to have the 5th expressed in it for added fullness of sound. The 9th adds just the right color on top.