Double String Unison (DSU) and Pitch Raises

Have you ever tuned a pitch raise, only to call the customer back and they say, “Your tuning was very poor so we asked someone else to come and retune it. They were much better than you.”?

This is a good reason for tuners to learn how to do the best pitch raises possible. Lately I have been using Double String Unison, P4 windows, and Parallel Octaves to do decent pitch raises in one pass.

Double String Unison (DSU) is a method of tuning a piano where the tuner mutes only one string and then tunes the other two until they sound good.

The two strings of a DSU are tuned together until they sound as a pure beatless unison, then the DSU is compared to another pitch. The comparison tells the tuner whether the DSU is good, or needs to be raised or lowered. The tuner then detunes the DSU by moving one string in the direction they want to change the DSU, then follows with the other string until the DSU is clean again, and then the comparison is made again until the tuner is happy.

There are many many advantages and pros to using the DSU method to tune a piano. The full DSU method I use involves a lot of peripheral techniques that make DSU very powerful.

Two such techniques are using the P4 window and using parallel octaves. DSU with these techniques allow me to perform an exceptionally good pitch raise in one pass!

The P4 window is a technique where I fit a M3, M10, and M17 into a P4. The M3 is used as a reference. The M17, P4 test creates a tempered or pure 12th. But it is the M10 that catches any drifting that may have occurred. This helps to “clean up” the tuning as I go along.

The parallel octaves are a method where I use two mutes as a DSU, one at the M10 and one at the M17. For a pitch raise, the M10 will always need to be corrected as one moves up the keyboard.

I also use the 8:4 window below the temperament, which is similar to the P4 window. The 8:4 window reaches up to E6 as we go down, creating clean single, double, and triple octaves, and correcting any drifting notes as I go along.

In this way, many notes are tuned three, four, and five times, before they are used as references to tune other notes. In this way, the tuning is much more efficient; there is much less cumulative error.

I recently tuned a K. Kawai grand piano that needed a pitch raise. I tuned it in one pass using this method.

Here is a recording of A#3 where one string is tuned and the other is original. This shows the pitch raise was from 436Hz.

Out of tune A#3 showing the size of the pitch raise; 4 beats per second at the fundamental.

Here is a recording of me playing an excerpt from Claire de Lune by Debussy and Giant Steps by John Coltrane after the tuning. I am 100% serious when I say that there was no tweaking of any notes whatsoever after the first pass. This is not that surprising if you understand how DSU, the P4 window, the 8:4 window, and parallel octaves all work together to result in many many retuning of notes within that one pass.

(My apologies beforehand for the poor performance.)

Claire de Lune – Debussy and Giant Steps – Coltrane

Note: The point of this post is not to show how someone can create a perfect tuning with only one pass. (I heard some bass octaves that were rolling) Nobody can do that, and achieving a perfect tuning is a challenge at the best of times. The point is that it is possible to create a reasonably good tuning with only one pass using these techniques.

7 Responses to “Double String Unison (DSU) and Pitch Raises”

  1. I recently had a doozy of a pitch raise to do – 1/2 tone. I tried using a more generic approach, fitting notes into fourths and fifths. It was a disaster. I went back to beat speed windows with high accuracy and tuning at 440. It was longer but I finished with a nicely tuned piano at concert pitch, with only one pass, but multiple corrections within that pass. Only possible with highly accurate beat speed windows.

  2. Christer Dirfeldt says:

    I did not understand this completely. With P4, do you mean a perfect fourth? How do you fit a M3, M10 and M17 in a perfect fourth? I am learning this craft by selfeducation by youtube, books and tuning pianoes. I use way too much time, but people are happy with their pianos, but i use a little etd in the temperament octave and check it and refines a bit with using chromatic M3’s. I tune octaves and unisons by ear. The best octaves I get is when I try to match the beatspeeds of the octave with the P12 below the upper in the octave. I think it is a type of mindless octave that Bill Bremmer talks about. I do pitchraises with the etd, and tries to calculate the overstretch so i am about +- 2 cent before final tuning, but using etd is slow because of the drifting of the needle. My goal is to tune all by ear when I believe that will go faster when I have learned it properly. I am thinking of, maybe, take an online course from you. I bought the book from Mario Igrec and it is really good, but over my head sometimes.

    • Hello Crister,

      Thank you for reading my blog.

      Yes, P4 means Perfect Fourth.

      The M3, M10, and M17 fit into the P4 like this:

      The test for the P4 is a M3 and M6 like this:
      Testing A3D4, use F3A3 and F3D4. The F3D4 should beat slightly faster than the F3A3. That proves the P4 is wide.

      Now, when tuning notes above the temperament octave, use this:

      Assume tuning A5:

      F3A3 beats same as (=) F3A4 beats slower than F3A5 = F3D4

      Also written as
      F3A3 = F3A4 slower than F3A5 = F3D4

      Heard as
      Slow – Slow – Fast – Fast


      F3A3 = F3A4 means A3A4 is a pure 4:2 which sounds best most of the time (But not always. See my lesson on beatless octaves.)

      F3A4 slower than F3A5 means A4A5 is a wide 2:1, which is the best size for these octaves most of the time.


      F3A5 = F3D4 is the test for the pure 12th

      All these beat speeds fit within the Slow – Fast speeds of F3A3 slower than F3D4, hence the P4 window.

      It really is much easier to show you.

      Search youtube for “Pure 19th howtotunepianos”. It is a video I made to show pure 19th tunings.

      My method uses DSU, NSL analysis, and Beat Speed Window. It is the most accurate, precise, and efficient aural tuning method ever devised.

      • Christer Dirfeldt says:

        Thank you Mark. If I got you right, that means that I tune my octaves a little too wide when I use slightly wide P12’s? I will definitely check your video on tuning by P12’s. It takes time to learn, I had not understand this at all for 6 months ago 🙂

        • Not necessarily. If you are tuning wide P19 when you are tuning wide P12, then all your intervals will be wide. Then, IMHO, that is too wide.

          Did you see my video on tuning pure 19ths? That helps keeps the 12ths all wide by the same amount. It produces wide everything else, but consistently wide. That seems to create a consistent treble tone for the piano, IMHO.

          Thanks for the questions.

          This method of using beat speed windows has some detractors, but they have not yet been able to show me the error of my ways. Since developing and using this method, tuning has become a simple as possible task for me.

  3. Christer Dirfeldt says:

    When tuning pure P19’s going up from temperament F3-F4, the first P19 is F3-C6. How do you test before that? And how do you tune and test P19’s going down from temperament? Check note is the same for both P12 and P19 but with slightly faster beat speeds for P19 then? And it is also the same check note as for P5 and 6:3 octave? Please correct me if I am wrong.

    • From F#4 to B4, tune pure or wide 4:2 within the P4 window, depending on the octave scaling you found when testing the F3F4 and A3A4 octaves for the temperament. (See lesson in beatless octaves)

      P4 window: C#3F#3 slower than or equal to C#3F#4 slower than C#3B4. (Proves a pure or wide 4:2, a narrow fifth, and a wide fourth.)

      From C5 to B5, tune pure 12ths.

      Note: the pure 12th/pure 22nd(triple octave) window also produces a pure 11th. You can start checking that at A#4.
      F3C#4 = C#4A#4.

      From E3 down, you can continue pure 19ths if you already tuned the treble, but the inharmonicity curve gets wonky around the break, so there may be more fudging between the sound if pure larger intervals like 12 and 19, and the simple octave.

      Pure 12ths in bass with pure 4:2:
      C4E4 equal C4E5 slower than C4E6 equal C4A4 equal E3C4 (pure 22nd)


      Pure 19th with pure 4:2,
      G3B3 = G3B4 slower than G3B5 = E3G3.

Leave a Reply

StudentBlog theme is brought to you by online slot games such as Plenty on twenty, Fruits and sevens and Columbus deluxe.