Chords sound plain? How to make seventh chords

Add a seventh: take your chord and stack one more note a third above the top note, staying in the key. C (C E G) becomes Cmaj7 (C E G B), Am (A C E) becomes Am7 (A C E G), F becomes Fmaj7 (F A C E), G becomes G7 (G B D F). It's the same progression, just softer and richer.

How to do it

1. Write your progression with plain three-note chords first.
2. For each chord, count up from the root: root, third, fifth, then add the seventh, the next note in the key above the fifth.
3. Keep the bass playing just the root so the low end stays clean.
4. If it gets too dense, leave out the fifth, it adds the least.
5. For even more colour, try adding the ninth on top.

Why it works

Triads sound simple and bright. The seventh adds a note that's close to the root, which gives a soft tension. That's the lush sound in neo-soul, lo-fi, R&B and jazz.