Ben C wrote:

This is something I've never understood. I don't bother with a
tensiometer myself, but surely if the spoke tensions aren't all about
the same then the wheel will be out of true?

This depends a lot on the rim and the spoke count. If you use a strong,
stiff rim with 32 or 36 spokes, for example a typical MTB wheel, you can
have one spoke a lot looser than the others without the wheel being out
of true - As long as the adjacent spokes are very tight.

On the other hand, if you build a front wheel with a lightweight road
rim and only 24 or 28 spokes what you say is closer to truth.

-as