Tuning Unisons

I don’t pretend to know everything about tuning unisons.

What I do know is that beginners should strive for the cleanest unisons possible. I also know that we do this by tuning the highest partials as still as possible. Because of the doubling effect of Hertz every octave, beating partials beat faster the higher they are.

For this reason, we are always focusing our ear to the higher partials of a unison while tuning it.

There has been some discussion among advanced level tuners regarding building unison tone. I know that two identical frequencies, while mathematically pure unisons, can actually add up to cancel each other out. I’ve had this happen before; tuned a unison so pure, it was quieter.

Anyway, some people refer to tuning unisons slightly out of tune in order to create more sustain and avoid the cancelling out phenomenon described in the previous paragraph. There are some websites that claim this technique works, but I don’t tune pianos, or for situations, where this is called for. I’m still working on getting clean unisons. 😉

So, while I don’t claim to know everything about tuning unisons, I do know there are some weird things happening with this unison I tuned. I was recording it and trying to produce a “blooming” or “opening” unison; one that grows and seems to sustain more than a beatless unison.

While this unison does not have a complete beat in it, there is a roll at each of the partials. What’s more, I seem to have been able to control which partial blooms or opens, and when.

Listen to this recording of me tuning a unison. As I tune it differently, different partials seem to open at different times. I am focusing on the 4th, 5th, and 6th partials, the major triad.

As I hear different partial melodies forming, I play the melody, and then the unison again. See if you can hear it.

My question is, what the heck is this? Why is it happening and is this what some call “building unison tone”?

Leave your comments below.


4 Responses to “Tuning Unisons”

  1. Forrest Halford says:

    at around 20″ I heard the second partial, C5 come into prominence after the initial strike. then later in the recording, it was the third partial, G5, and then even later in the recording the 6th partial, G6. The bloom happened in each case after the initial strike.

    Was this the strings synching with each other, or after the initial hit, coming into synch?

    Is this caused by a hammer mating issue, or is it a natural way for the strings to behave?

    I never could discern either the 4th or 5th partials, even with headphones. The most pleasing to me was the prominence of the 2nd partial.

  2. Cobrun Sells says:

    I believe that since the strings can differ in tension, length, and diameter even as small as possible the differences in those three variables changes inharmonicity for each string in a unison. And since each partial increases and decreases in amplitude at different times I feel that there is much confusion between the upper partials even between two strings of a unison. Add on top of that the phasing of two separate strings.

    • When we learn to listen more closely to the piano strings and their individual partials, there are truly amazing things to be heard.

      Recently I discovered an amazing phenomenon. There is controversy about the effect on the pitch of a single string by adding a 2nd string in unison. Gabriel Weinreich discovered this phenomenon and it is called the Weinreich Effect; the pitch of a single string can go up, down, or stay the same when a 2nd unison string is tuned to it.

      Tuners concerned with accuracy and efficiency know this is not fantasy and use methods to deal with this. (See my DSU method for example)

      However, I have been measuring the effect of adding a 3rd unison string to an already tuned double string unison. The results are shocking to me; a similar effect as Weinreich observed.

      The conclusion is clear; as technicians who want accurate and efficient tunings, when using open unison techniques like DSU, we need to assess the correctness of the final trichord before moving on.

      I had been confused by the apparent drifting of trichords I’ve tuned but now they are much more stable since I’ve been checking the trichord as well before moving on.

      If I find a problem like a drifting in pitch after adding the 3rd string, I mute one string and shim the double unison in the direction I want to go. Now if I test the double unison, it doesn’t fit, but once I add the 3rd string, it drifts to where I want it.

      It may be more accuracy than most technicians are interested in, but I love that I can anticipate and control the pitch more than I used to.

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