The five-string banjo can be one of the most difficult instruments to keep in tune. There are a number of reasons for this. The neck is long, relatively thin, and more flexible. The head is very thin and has a certain amount of “give” to it, depending on how tight it is. The bridge is movable and can easily be bumped out of place. The strings, light or medium gauge, are under fairly low tension compared to other stringed instruments. With all the violent activity brought on by the metal finger-picked right hand, the strings take quite a beating. And, here is another aspect that makes tuning a challenge: a number of standard bluegrass licks played within the 1st five frets require sliding or hammering to the same note as an open string, i.e., 4-5 slide on the 4th string, 2-3 hammer on the 2nd string and 2-5 slide on the 1st string. Because of the relatively bright tone of the banjo, these “moves” will sound pretty sour unless you are perfectly in tune. And, we haven’t even put a capo on yet! Sounds like fun, huh? All is not lost. It’s important to identify these possible trouble spots. A proper setup will take care of most of them. Make sure the neck is firmly attached to the rim. With proper head tension and tailpiece adjustment, tuning distortion can be minimized. Check for loose tuning pegs.
Now we can set the bridge. First, use a fresh set of strings. In theory, the 12th fret is the halfway point between the nut and the bridge. In reality, it will not be so, but that’s a good place to start. After tuning as close as you can with a good electronic tuner, check the harmonic at the 12th fret versus the fretted note at the 12th. If the fretted note is higher, move the bridge back toward the tailpiece. If the fretted note is lower, move the bridge forward toward the neck. You may find that the 1st and 2nd notes are true but the 3rd is out, sometimes way out. Usually, the 3rd will be noticeably sharp. Try slanting the bridge a bit so that the 5th string side is closer to the tailpiece than the 1st string. In some extreme cases, a compensated bridge may be the answer, or some minor compensation on a regular bridge, if it’s thick enough, will help. If your action is much higher than standard, you will have a tougher time dialing in your bridge location.
When you find a location that works well for you, make a pencil mark around the outside feet. This will help during string changing. Keep in mind that if you change string gauges or bridge height, you will need to relocate the bridge somewhat. This can be a frustrating procedure. If you are still having major tuning problems, run to your nearest repairman.