My father is trying to fix a tenor banjo which we bought some years ago, but which has not been played a lot because it doesn’t work properly. The problem is that, for some reason, the notes on the first four frets on the thickest string sound a bit sharp, no matter how we tune it. The other strings are fine. The neck is perfectly straight and the frets don’t seem to be uneven. Dad has tried lowering the strings, tightening the skin and eventually putting thin pieces of plastic between the frets. The tuning has improved a little, but these notes are still slightly sharp.
Does anyone have an idea about what might be the reason to this problem, and how to fix it? I’d be very grateful for answers!
What tuning are you using, standard (C) or Irish (G)? In Irish tuning the tenor banjo is playing at the lowest possible tension and very often the bass string can sound a bit off. Have you tried different string gauges for the lowest string? Also, you may need to angle the bridge slightly with the bass side a little closer to the tailpiece than the treble side. That changes the open string length for the heavier strings slightly. Do you get perfect octaves at the 12th fret? If not you’ll need to make that adjustment also.
Thanks Tim! I’ll try out your suggestions about string gauges and angling the bridle. I use Irish tuning so it sounds very likely that these could be just the things to do.
I don’t know about the octaves, never having tried it out with a tuner, so I’ll have to test that also. How do I adjust it if the octaves aren’t perfect?
For any stringed instrument with a floating bridge (one not glued down), you have to place the bridge so that the intonation is correct. First get the bridge close to its correct position using a ruler. The distance between the nut and the 12th fret should be nearly the same as the distance between the 12th fret and the bridge (the 12th fret cuts the string in half). A banjo’s bridge is normally about three inches in front of the tailpiece, not in the middle of the head. Then tune the highest and lowest strings to their correct pitches. Now play the strings at the 12th fret. These notes should be exactly one actave higher than the open pitch. If they are sharp, slightly loosen the strings to reduce the tension and move the bridge slightly toward the tailpiece (lengthen the string). If they are flat, move the bridge toward the neck (shorten the string). Retune the open strings and test the pitch at the 12th fret again. Repeat until the 12th fret is exactly an octave higher for both highest and lowest strings. It may take several tries. You may find that the bridge has to be angled one way or the other to make both ‘sides’ of the instrument in tune when open and at the octave. Also be sure to check that the bridge is not ‘falling over’ when you do this. It should be straight up and sitting squarely on its ‘feet’.
This procedure sounds complicated, but you’ll get good at it with a little practice. It’s something that needs to be checked frequently and adjusted from time to time. Whatever you do, don’t glue the bridge down. It must be allowed to float, even if it does change position sometimes. Some players like to make a faint pencil mark on the head of the banjo to mark the location of the bridge. That helps when checking the intonation, but the position is likely to change when you use new strings or different gauges.
Believe it or not, we did it! A match under the nut, a little work with the bridge, and Bob’s your uncle! (Well, he’s not, actually. My uncles are called Harald and Holger, but that’s another story…) Anyway, it’s a much better banjo now, and a lot more fun to play.
I’d be very grateful for answers!