Originally Posted by
sblock
There are quite a few reasons why a mandolin doesn't stay in tune. Some of these have already been mentioned, some not.
1) The truth is that many mandolins, particularly those new ones that cost less than around $1,000, tend to be poorly set up at the factory. As a result, the action is often too high, or the strings will tend to bind at the nut or the bridge, and so on. Many tuning problems on such instruments are ultimately traceable to a poor setup. ALL mandolins need to be well set up. All nuts need to allow the strings to pass freely and not to bind. This is probably THE most common tuning issue, IMO.
2) Yes, some tuners can grab or slip. This is especially a problem with some of the older tuners (like those on older Gibsons, from 1900-1960). Often, lubrication and cleaning can help. Sometimes older tuners may require replacement altogether. But tuner problems can also happen on newer instruments, too, especially when the tuner bushings are not in proper alignment. But most modern tuners, when properly installed, will NOT cause any problems. That doesn't stop folks from blaming them, though! Also, some tuners have loose buttons or more hysteresis/backlash, but always tuning UP to the note from below (and never down!) avoids any issues associated with these problems.
3) Some folks don't properly attach the strings to the tuners at the posts (with enough windings around the post, or with overwinding, or with a luthier's knot; there are many ways to do this right), or at the tailpiece, leading to string slippage. This usually results in sudden de-tuning, but it's also possible for strings to slip more slowly, and therefore go a bit flat over time.
4) Yes, our ears are much more sensitive to hearing tuning that's off when there are double courses, as is the case for the mandolin. Even a few Hertz of difference (a few cents of pitch) can produce audible beats between the strings of a given course when the strings are new. And when the strings are older, they may not "move into" the note at the same rate, and sound bad for that reason.
5) On top of that, our ears are more sensitive to minor pitch differences in the higher ranges -- like on the mandolin. It's much harder to detect small frequency differences in lower pitches. You can be rather far off-pitch with a bass guitar, for example, and it will still sound reasonable to most people. Bassists get away with murder.
6) Mandolins have short scale lengths and they are therefore more sensitive to small temperature differences (including, even, the heat imparted by your left hand while playing). They are also more sensitive to small changes in humidity. Higher humidity will cause wood in the neck to swell and make the notes go sharp. Mandolins made entirely of synthetic materials, like carbon-fiber, tend to be more immune to changes in temperature and humidity, and they stay in tune much longer! But most of us still like the sound of wood.
7) Yes, mandolins constructed with a lighter build may move a bit more than those with a heavier build (for reason #6, temperature or humidity changes), and thereby go out of tune. But I don't think this is such a big effect, personally. There is also the permeability and type of the finish to consider, which can also show effects due to changes in humidity.
8) Old strings just won't stay in tune. They tend to go flat when first hit, then rise slowly into pitch. You can see this clearly with an electronic tuner. Old wound strings may have bits of the winding worn away on the undersides, where they contact the frets. Old unwound strings may show visible kinks at the lower fret positions when you remove them. When tuning problems start to get worse, it's usually a sign that you need to change your strings.
9) Poor-quality strings won't stay in tune, either, or they may tune reasonably well when unfretted, but then give the wrong-pitched note at some frets! This problem is caused by strings that have non-constant diameters, due to bad pulls through the die while they were being formed, or to irregular windings, caused (for example) by variations in winding tension when they were made. Ir variations in the diameter of the winding wire. Always use high quality strings -- and avoid buying cheap, counterfeit strings.
10) The short scale length combined with high string tensions on the mandolin mean that extremely tiny changes in tuner post angle will translate into large changes in the string pitch. Put another way, mandolin tuners are extremely sensitive! Some tuners have 16:1, 18:1 or even 20:1 gear ratios, because the higher ratios can alleviate this problem. A bit. But the truth is that, regardless of the tuner ratio on your mandolin, you need to learn to make the TINIEST changes with the tuner knobs, sometimes just a degree or two, using the lightest possible touch to turn the posts. This is definitely a learned skill that gets better with practice.
11) And, of course, newly installed strings will stretch and go flat for a short while. You can pre-stretch these a bit with your hand (but don't overdo it!) and speed up the process.
But the bottom line is that if you play mandolin, you can look forward to to a lifetime of tuning and re-tuning. It's part of the job description, don't ya know?
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