Harmonic tuning is a very accurate, very quick, and very easy way to tune a bass in fourths. (Standard tuning)
I'm going to assume that anyone reading this is already familiar with what harmonics are, and how to play them. If not, that's something to be covered in another thread, which you'll have to be familiar with first.
Harmonic tuning is a method of
relative tuning. This means that all your strings will be in tune with each other. But they may still be out of tune. You need to be certain at least one of your strings is in tune before you start harmonic tuning, if you're going to be playing with anyone else.
As you probably know, the harmonic over the 5th fret is identical to the harmonic over the 7th fret on the next string up. This is the basis of harmonic tuning. Play the two harmonics together.
<7>
<5>
If the two strings are perfectly in tune, you will hear one, pure tone. If they are out, you'll hear an odd phase effect. The note will seem to pulse. The slower the pulse is, the closer the strings are to being in tune. Adjust the tuning until the pulsing slows down, and ultimately stops.
That's all there is to it.
If anyone's interested, I can explain
why the pulsing effect occurs, but it's not necessary to know that to be able to tune harmonically.
*****
Important note - the harmonics are only the same note if the bass is tuned in fourths (EADG). If other tunings are being used, harmonic tuning can't be applied.
Example - if you're tuned in Drop-D tuning (DADG), harmonic tuning can be used to tune the A, upper D and G strings, as they are in fourths. You'll have to use other methods to tune the lower D string, though. (such as a tuner, or conventional ear tuning)