Bridge angle

[sanmenxia]

tansungwah.blogspot.com/ has some interesting comments re the angle of the bridge.

The erhu teacher/player at the London summer school also has her bridge set up this way. I've been thinking about the possible reasons why it would be set up like this. Doesn't the violin/cello have their bridges placed at right angle to the strings? i.e. the sounding length of all the strings is the same. But I think this unequal erhu string length set up might be more related to the way guitars are set up because on the erhu the finger stops both the string at same place from the nut (qianjin), just like a fret on the guitar. From what I have read, a guitar bridge is placed at an angle to account for the difference in the amount of increased pitch of the strings when they are pressed against a fret, if you bend a thin and thick string by the same amount, the thin string will increase in pitch more than the thick string. However could it be that the bridge set up on a violin doesn’t need this compensation because the player plays on each string with a separate finger and can adjust their intonation on each string.

Thinking more about it…shouldn’t the erhu bridge actually be set at a clockwise angle? Because it if was anti-clockwise, as in the blog, that means the thinner A string is shorter so the pitch will go up even more.

Anyway I think this only affects playing in very high position and then only when the thicker D string is played with same finger as on the A string.

I’m just speculating about this, I may be completely wrong!

[song]

I have no idea as well. Perhaps Maaltan might have a scientific explanation for that.

The one who told me about the bridge actually mentioned the late great Banhu player Liu Ming Yuan (the one who wrote the tune 'Xi Yang Yang') has his bridge turned clockwise instead.

I have to ask him why the next time I see him.


Sung Wah

[simon18i]

my teacher also tunes the bridge clockwise direction. i noticed he does that to elliminate noise. if according to sanmenxia, the bridge indeed should be tuned clockwise. in my opinion the other players tuned their erhu counter clockwise is to increase the range of the erhu, so they have a lower low and a higher high note.

[jetz320]

If this helps with tuning, this may be a good trick.

For me, on both my erhus, the A string is what always get out of tune the quickest.

[sanmenxia]

Thinking about it now, I can’t actually remember which direction the summer school teacher had her bridge. I know another player who has the bridge turned at an angle, but again I can’t remember which direction.

I think it’s very interesting that some players turn it one way and others turn it the other, and also that Liu Mingyuan agreed with me So far we’ve had 4 theories; to increase range, to stabilize tuning, to eliminate noise, and to compensate for intonation. I think we can rule out the first and second, I don’t think the difference in the angle of the bridge affects the range of the erhu nor whether or not the pegs hold their position. The second is possible but if my thinking is correct, it’s not the main reason for turning the bridge.

Now for the last one, if it is done to compensate for intonation, then I think it should be turned clockwise. This is so that the interval between the two strings remain a fifth where ever up the string is stopped. If the bridge is set at right angle, the interval will get progressively wider up the string. If you played a note on the A string with good intonation, then the note on the D string with finger stopped in the same position will be flat to varying degrees depending on how high the note is. In the first position (nearest to nut), it will not be significant but as you played higher up the string nearer to the bridge the interval between the two strings will get wider and wider. To compensate for this, the direction to turn the bridge should be clockwise.

I’ve tried a bit of experimenting with my erhu and ap tuner and it seems to confirm my thinking. Also the bridge on a guitar has the bridge set at an angle with the higher string longer and low strings shorter, well on acoustic guitars anyway.

This must have been already discussed by Chinese erhu or huqin players, perhaps on Chinese online forums?

[song]

sanmenxia said:

Now for the last one, if it is done to compensate for intonation, then I think it should be turned clockwise. This is so that the interval between the two strings remain a fifth where ever up the string is stopped. If the bridge is set at right angle, the interval will get progressively wider up the string. If you played a note on the A string with good intonation, then the note on the D string with finger stopped in the same position will be flat to varying degrees depending on how high the note is. In the first position (nearest to nut), it will not be significant but as you played higher up the string nearer to the bridge the interval between the two strings will get wider and wider. To compensate for this, the direction to turn the bridge should be clockwise.

I've never really noticed that the inner string would be slightly flat when the bridge is set at right angle.

Well, if setting it at a right angle maintains the fifth between the 2 strings, then turning the bridge clockwise or anticlockwise would disrupt the interval between the two strings at the higher registers, thus making it impossible to play certain tunes in tune.

Or perhaps the difference is too minute to be noticed?

[davidmdahl]

sanmenxia said:

<snip> If the bridge is set at right angle, the interval will get progressively wider up the string. If you played a note on the A string with good intonation, then the note on the D string with finger stopped in the same position will be flat to varying degrees depending on how high the note is. In the first position (nearest to nut), it will not be significant but as you played higher up the string nearer to the bridge the interval between the two strings will get wider and wider. <snip>

I have been thinking about this, and have come to the conclusion that it does not make any sense to me. In my experience, two or more strings tuned to a perfect interval stay tuned to that interval regardless of where the strings are stopped. Guitar strings are tuned to an even wider distance than erhu strings, and yet harmonics played up on the neck are perfectly in tune from one string to the other.

If the erhu bridge is turned one way or the other from "normal", it will change the tension required to tune the string ever so slightly. It is hard to say under what situations this is beneficial if it is even noticable.

I have noticed that there are a lot of hard-to-explain hocus pocus techniques that people use on musical instruments that supposedly improve something or other. If it works for you, by all means do it.

Best wishes,

David

[sanmenxia]

Harmonics of course will always be perfectly in tune, but things are different when you stop strings by bending them. When you bend a thick and a thin string at a certain point by the same amount, eg stopping two strings at the same fret on a guitar or stopping two erhu strings with one finger, the thick and a thin string will increase in pitch by different amounts. Apparently this is why guitar bridges are not set at a right angle, or need mechanisms that can adjust the sounding length of each individually.

In practice though, intonation is not an exact thing anyway, so all this might be not noticeable, all you can say is if it sounds in tune then it is!

I still think it would be interesting to find out how common it is for erhu/huqin players not to set their bridges at right angle and the reasons why.

[davidmdahl]

There is a good description of the situation on the guitar at the following link:

members.aol.com/rogluthier/indextune.html

On a steel-string guitar, the bass strings are set higher, due to their thicker diameter, and need to be pushed further to the fret. That extra distance raises the pitch a little higher than a thinner string that is set lower, unless compensated for.

I don't see how this is an issue on the erhu. The strings are not that different in thickness, and are not set at different heights. We don't really push that hard on the strings. Any difference in tuning at the higher positions would have to be so small that they would be compensated for by the player without even thinking about it.

My erhu teacher also plays violin. I will ask him if he knows anything of this.

Best wishes,

David

[calden]

I wouldn't think this kind of adjustment would make a lot of difference except to an expert who can really play well up the neck.

In the world of banjos there are a lot of people who purchase expensive bridges that compensate for the string thicknesses, the fact that there is a high-tuned string way over next to the low tuned string, the skin head that changes the pitch, the phases of the moon, and what color underwear one is wearing when they play. This stuff, for me, falls in the category of "fuss with the details instead of playing it."

Technically, one could alter the rotational position of the bridge on the erhu to correct for minute differences in pitch caused by string thicknesses. However, especially on erhu, there are so many other controllable factors that cause pitch variations (finger placement, finger pressure, vibrato technique, stress put on neck when holding the instrument, and tiny pitch variations intrinsic to the instrument really only show up the higher up the neck you play.

Carlos
Not meant to sound too grumpy, I just need another cup of coffee, or a trip to China

[song]

Actually, the initial explanation that I thought of regarding turning the bridge to keep the strings in tune is that by turning the bridge at an angle, the grooves on the bridge 'locks' the string in place, making it less likely to slip out of tune ever so minutely.

makes any sense from a physics point of view?



Sung Wah

[calden]

Yes, makes sense. Also consider that if the strings have at all enlarge the grooves (tuning, wear and tear, etc.) then slightly turning the bridge will not only lock the strings in place as you say, but also narrow the groove a bit and take out any slop. Less slop = tighter fit between string and groove = more contact between string and bridge = more string energy going into sound production, and also less chance of buzzes, blips, whines, etc.

Carlos