Rules of the road

Need a definition? Tap or click a dotted word. You can hear examples there, too.

What to avoid, and why

and : two voices a perfect 5th (or ) apart moving together to another 5th (or ). They fuse into one voice, and the texture thins out.
Voice crossing: a lower voice jumping above a higher one blurs the lines.
The in the top voice should rise to the at a .

These are style rules for clear four-part writing, not laws of nature - rock guitarists use (power ) on purpose.