Unwanted overtones

[A5Dave]

I play a Loar LM400, the A-5 style, with a brass tailpiece. I am getting overtones that I can't get rid of. When I play a D on the A string the 12th fret harmonic on the D string sounds, as well as the 7th fret harmonic on the G string. This kind of thing happens all over the instrument. I have leather wrapped around the strings between the tailpiece and bridge. Ideas ??

[Givson]

Put an additional strip of leather between the strings just above the nut.

[John Flynn]

I think that happens to some degree on a lot of instruments, although on most it is too slight to notice. It was really bad for one note on my Rigel when I first got it. The leather strips on the tail and head strings did no good at all because the sound was coming from the open strings in the playable area. I found it lessened as my strings got more broken in. I got some relief from trying different kinds of strings. I also found that I only really noticed it when practicing tunes slowly on my own. When I was playing up to speed with other people, It was probably still happening, but I never noticed it. As the Rigel got older and "broken in" it stopped happening. If you ever considered upgrading your bridge, that might help, but that is a total shot in the dark.

[Willie Poole]

I have seen this happen when using bronze strings but not with phosphur bronze strings, must have something to do with the way thay are wrapped....Play it for a while and see if it gets less as the strings get older and coated with oil from your fingers...

[Tim2723]

Willie beat me to the draw. I've had it happen with one set of strings and then not another. I don't remember if I was using bronze strings or not, but see if it gets better as the strings break in and then change strings to something else and and see if it comes back. I didn't think this had ever happened to anyone else. Weird.

[A5Dave]

Thanks to all who've responded...I've added the extra strip of leather above the nut to no avail. I will say that this problem is accentuated by the new J74's I've just put on, so will wait and see what happens as they age . That said, however, I usually use Elixir 11525's (the medium guage) , and the problem is lessened by age, but not eradicated. I have not recorded with this mando and this problem, so I don't know if the overtones would be heard on tape. It is not a major concern when playing live, just a minor irritant.

[Tom Wright]

Damping unused strings is useful technique (except when you want the extra ringing of sympathetic strings). Damp as needed with either palm or left hand fingers. The latter is sometimes done by deliberately fingering so that you bump against the neighboring string, or by using a different finger extended across.

New strings are less fatigued and will ring more easily, especially any type that is bright. True flatwounds will ring much less, being naturally more dull in the highs. But the answer is in the playing, although in practice you won't hear the effect even on a recording except in the most spare and quiet textures.

[shawnbrock]

I always have the strip of leather behind the nut to kill the tones up there. It sounds to me though like this is more of an attribute of "sympathetic vibrations". Keep in mind that when in tune each note should trigger vibrations from another note. This is part of what makes up sustain, and mostly is a good thing. For example if you play the D note (5th fret on the A string), and leave your D string open, you should be able to touch it with one of your other fingers and feel the slight vibration of the string. The open D is activated by the D on the A string, the open G will be as well... That's not to say that it don't get annoying at times, but there are reasons for this which makes it more of an asset than a problem, most of the time... It may be worth trying some J75s to see if that makes any difference. Different gauges and materials of strings can make a change in these kinds of things. The larger the string, the slower the vibration which is called "oscillation". Sorry, it seems like I'm over complicating things and turning this into a science class. And all you were wanting to do is get rid of a harmonic and play the mandolin... You may also consider moving around your leather or other muting material behind the bridge. On some mandolins this makes a lot of difference. Some sound funny if the leather is near the bridge, while others sound better when the leather is almost riding the bridge. Seems though like you may be cursed with a well tuned box/ tone chamber. Which is a good thing! I better go before I start in on the Harmonic Series...

[mandroid]

Resting my hand lightly behind the bridge, as I do, I've never heard any ..

[Polecat]

Tune your mandolin in tritones and learn new fingering...

Levity aside, I suspect that one reason most stringed instruments are tuned in fifths is to ensure that the unavoidable sympathetic resonance of other strings sounds harmonic (guitars and basses are also tuned in fifths, if you think about it). In my opinion, the strings are probably meant to sound when you play a D on the A string, if you play an open E then damp the string you will hear the first harmonic on the A string. And so on...
Purely out of curiosity, why does this bother you?

[John Flynn]

Purely out of curiosity, why does this bother you?

I can't speak for the OP, but when this effect used to happen on my Rigel, it was so pronounced that those harmonics would keep ringing on into the next note(s) I was playing. So to use the scenario the OP outlined, he has just played a D (5th fret) on the A course that has causes D's to ring on two other courses, the open D and the G. What if the next note in the melody he is playing the next fret down, a C# on the A string? That C# will not cause a sympathetic vibration that will cancel those D's out, so he is now playing a C# to what is in effect two D "drones." That will obviously be very dissonant. The sympathetic vibrations I had were on different notes, but the effect was the same. It could make some tunes sound pretty bad.

[Tim2723]

The terms sympathetic vibration and overtone are often used interchangeably, but which are we actually talking about?

[Polecat]

Both: When I play a D on the 5th fret on the A string I produce a note with a frequency of 587.33 Hz (at least in theory); that is the 1st harmonic (overtone) of the D string, and the 2nd harmonic of the G string. In other words, the D string starts to resonate as if it were stopped exactly halfway along its length, and the G string as if it were stopped at 1/3 and 2/3rds. If I play a D# on the A string, no doubt there are harmonic equivalents on the other open strings, at least as far as the overtones of the D# are concerned, but they are energetically negligible, which means I won't hear them whilst playing.
That is the theory; in practice, there is a norwegian instrument called the hardanger fiddle that has sympathetic strings running under the fingerboard that resonate with the melody, and it takes a little time to get used to the sound it produces (although most of the tunes I've heard for this instrument are strictly pentatonic). I can't think of a tune that I play on the mandolin where the sympathetic notes on the open strings sound dissonent - perhaps someone can suggest one.

[John Flynn]

The terms sympathetic vibration and overtone are often used interchangeably, but which are we actually talking about?

I am not an acoustics expert, but I think we are talking about both. Wikipedia says, "Sympathetic resonance or sympathetic vibration is a harmonic phenomenon wherein a formerly passive string or vibratory body responds to external vibrations to which it has a harmonic likeness." So the "formerly passive strings" are the un-played open strings. Those strings vibrate on a harmonic of the played note. So the D strings sympathetically vibrate to their octave harmonic because a D is being played. The G strings sympathetically vibrate to their perfect fifth harmonic, also a D.

[Tim2723]

Oh, OK. That would be both. It's not just the string lengths between tailpiece and bridge, but the playing (vibrating length) that's the problem.

[hank]

Ok then is this also what's driving the strings to vibrate behind the bridge and nut?

[John Flynn]

Ok then is this also what's driving the strings to vibrate behind the bridge and nut?

Yes. It's all sympathetic vibration. But those lengths of strings are shorter, so they will tend to have less sustain and they are less likely (although I'm sure it happens) to be "tuned" to a harmonic of a note being sounded.

[Paul Statman]

I would try a set of Gibson Sam Bush monel, and/or GHS Silk and Bronze. Having a drier sound, they are not as 'zingy' sounding as the bronze varieties, and may be more simpatico and less sympathetically vibrationous!
Hope this helps.

[Marty Jacobson]

One thing that I think has not been mentioned is that this can be a symptom of a poorly cut nut slot. You might want to check that out, especially since changing strings often requires refinement of the nut slot (if you are changing types of strings or gauges).