Thank you for the clarification, Philippe. Even though I read the manual and tried various configurations based on it and some comments from this forum and other sites, I think it's important that this explanation be added to the manual. It was great that it was explained in that way, but I didn't manage to find that response because it was from 2013.

Lemuel, you are perfectly right, my fault, we need to make this clear in the manual.

Lemuel wrote:

But here's the issue, their default settings don't match reality. Take the Steinway D: Pianoteq defaults to a maximum string length of 2.70m, when the actual Steinway D measures 2.01m. That's nearly 70cm shorter in real life!

Thank you Lemuel for your contribution!

Regarding this length question, I agree it is a bit tricky/confusing, but do not worry, the string lengths are set correctly in all pianos, please read this following old post: https://forum.modartt.com/viewtopic.php...93#p928593

That confirms BTW what YvesTh wrote above. Sorry for the confusion.

Thank you for the clarification, Philippe. Even though I read the manual and tried various configurations based on it and some comments from this forum and other sites, I think it's important that this explanation be added to the manual. It was great that it was explained in that way, but I didn't manage to find that response because it was from 2013.

If possible, please consider adding these parameters in future updates or maybe Pianoteq 10: "decay time of each key, meaning the on-note decay and sustain of each harmonic in each key" and "unison detune on each key." These are some suggestions my friend mentioned to get even more configurable settings and achieve a more realistic sound, potentially replacing sampled libraries with modeled pianos in some way over the long term.

I wanted to customize the sound by combining a few parameters to reach a result similar to what that new parameter suggested by my friend would achieve, but in some way it feels like hitting a dead end. Yes, we know it's modeled technology where every parameter change affects everything and consumes more CPU, even nowadays. However, if you know of any combination of parameters we can use to achieve an even more customizable and realistic sound in these years before the release of Pianoteq 10, that would be great. Or please consider adding them in future releases of Pianoteq 9, even if it's only in the Pro version.

It's hard not to appreciate Pianoteq. It's great with low resource consumption (CPU, RAM, SSD) and high-end new instruments every few months at reasonable prices compared to VSL pianos. My friend said in the past, "I have the best pianos... VSL and Pianoteq." has pianos from more brands but uses them only occasionally.

Something important is the Delay and Reverb settings. Yes, Pianoteq implements algorithmic reverb, but it could benefit from new presets by default and use more mics like in my last preset "L7 Natural (Dec 27)," which is still in FXP Corner in this forum. This post with the new release was a test of the new Stretch Curve based on new formula implementation, research, and many other things which I adjusted to optimal parameters in the mode Alexis mentioned. Maybe in a future release with new data until January 2026, it can sound a bit better than the default curve in Pianoteq 9, at least on the Steinway D with the settings you said are right as defaults. I will then use the default string length with the default value of 2.70 m.

Thank you in advance.

But here's the issue, their default settings don't match reality. Take the Steinway D: Pianoteq defaults to a maximum string length of 2.70m, when the actual Steinway D measures 2.01m. That's nearly 70cm shorter in real life!

Thank you Lemuel for your contribution!

Regarding this length question, I agree it is a bit tricky/confusing, but do not worry, the string lengths are set correctly in all pianos, please read this following old post: https://forum.modartt.com/viewtopic.php...93#p928593

That confirms BTW what YvesTh wrote above. Sorry for the confusion.

Well, for the most part, people will find a piano with Octave Formula 4:2 (range: Db3 to C4 or Eb7 to C8) should work with every tuner by default like a strobe tuner, to get Cents Deviation from 12-TET Equal Temperament (Whole numbers), and that was the problem.

In that range we could find Key 37 (A3). Length (m) = 0.773. Steinway D measurements in 2012: Reference: Juliette Chabassier & Marc Duruflé, Physical parameters for piano modeling, INRIA Technical Report RT-0425 (2012). ⟨hal-00688679v2⟩ https://inria.hal.science/hal-00688679v2

In a stretch curve like the default by Modartt, using Advanced Tuning > Stretch > Transfer the stretching into Detune note-edit. While this option allows you to see how Pianoteq selects the appropriate tuning based on inharmonicity, the explanation is only partially correct.

Because, when you compare User Interface of Pianoteq vs. Measurements, well there is a discrepancy. And that discrepancy is needed to give even more realistic sound. And it could be useful to get total string length from I don't know 0.01 m for example to 10 meters actual maximum value in Pianoteq 9.

Sorry for mistaking you for an AI.
I don't question the theory of inharmonicity related to string lengths, the theory of stretching. I have read a lot of books on piano tuning and acoustics in general, and I agree with all of that. Where I disagree with you is solely on your assumptions that Modartt would not apply these theories... String length for exemple (see the Alexis answer)

Look, I did the math, and honestly, I’m done with this topic. For those octave-matching variables you’ll need an extra formula to get accurate measurements; otherwise use dedicated tools like TuneLab 5.3, Verituner 4.1, PianoMeter, etc. . There’s just too much calculation involved to chasing a marginally “more realistic” sound.

I feel like I'm communicating with an AI. Please read Alexis's response.

No AI will simply tell you "You are absolutely right!" just because Alexis suggested using Advanced Tuning > Stretch > Transfer the stretching into Detune note-edit. While this option allows you to see how Pianoteq selects the appropriate tuning based on inharmonicity, his explanation is only partially correct.

Yes, A0 = -15 cents and C8 = +42 cents are reasonable values for the User Interface when applying that option as Alexis suggested. However, compared with real-world measurements, these values are still inaccurate.

To illustrate: when measured using Reaper 7.58 (DAW) with the VST3 plugin LockOn 1.0.4, the results are A0 = +5 to +7 cents and C8 = +48 to +50 cents. This discrepancy reveals that the formula is still incorrect. The value displayed in Pianoteq's interface (A0 = -15 cents) differs significantly from real-world measurements (A0 = +5 to +7 cents in LockOn). This is the core problem.

If you check each key from A0 (2.01 m string length) to Ab3 (0.816 m) using the string length data I shared previously in this post, you can verify that any measurement hardware or software will yield more accurate real-world values, in a real Steinway D.

Regardless, for those interested in reference data, I recommend consulting the Railsback Curve (1938) and Precision Strobe measurements:
http://www.precisionstrobe.com/apps/str...teind.html

Data for Future Calculations in Pianoteq

Octave Matching Formula (A4 = 440 Hz):

• 10:5 - A0 to Ab1

• 8:4 - A1 to E2

• 6:3 - F2 to C3

• 4:2 - Db3 to C4

• 2:1 - Db4 to D7

• 4:2 - Eb7 to C8

String Lengths (in meters, A0 to C8):

[2.010, 2.009, 2.008, 2.007, 1.997, 1.981, 1.965, 1.938, 1.911, 1.879,
 1.842, 1.805, 1.762, 1.709, 1.655, 1.602, 1.548, 1.495, 1.442, 1.378,
 1.837, 1.757, 1.660, 1.591, 1.482, 1.403, 1.329, 1.259, 1.192, 1.129,
 1.070, 1.013, 0.960, 0.909, 0.861, 0.816, 0.773, 0.732, 0.694, 0.657,
 0.622, 0.590, 0.559, 0.529, 0.501, 0.475, 0.450, 0.426, 0.404, 0.383,
 0.363, 0.344, 0.326, 0.308, 0.292, 0.277, 0.262, 0.249, 0.236, 0.223,
 0.211, 0.200, 0.190, 0.180, 0.171, 0.162, 0.153, 0.145, 0.138, 0.130,
 0.124, 0.117, 0.111, 0.105, 0.100, 0.095, 0.090, 0.085, 0.081, 0.076,
 0.072, 0.069, 0.065, 0.062, 0.058, 0.055, 0.052, 0.049]

Cents Deviation from 12-TET Equal Temperament: (Whole numbers)

Anyway, if you want more information consult my post: https://forum.modartt.com/viewtopic.php?id=12942

Good luck, man.

PS Juliette Chabassier (whose work you cite) is part of the Pianoteq development team, so you should revise some of your assumptions..

No, the inharmonicity of the strings in Pianoteq is not calculated for all strings with a length of 270 cm. The length indicated in Note Edit is the length of the piano, not that of each string. It would be impossible and unrealistic to obtain a realistic high note with such a length. You are underestimating Modartt; within the model, all the strings are obviously different, length and diameter but not accessible...
As for measuring frequency with a tuner, I did it virtually in a DAW. And as with an acoustic piano, the accuracy has its limits because a string does not vibrate at a perfectly stable frequency, so any tuner will give an unstable measurement. This is further proof that Pianoteq models the acoustic behaviour of a piano very well. Furthermore the value of stretching Is not the same for all instrument even of same model, it Is the choice of the technician, so +20 or +30 are choices.

To add to the research: Pianoteq’s user interface uses an impractical string-length range. The editor only allows string lengths between 0.80 m and 10.00 m, so any real piano strings shorter than 0.80 m cannot be entered, even for extreme treble notes. That’s a problem for modeling instruments like a Steinway Model D, where many treble strings are far shorter than 0.80 m.

I extracted real Steinway D measurements from the INRIA technical report by Juliette Chabassier and Marc Duruflé (Physical parameters for piano modeling, RT-0425, INRIA, 2012; ⟨hal-00688679v2⟩). I truncated each value to two decimal places (I removed the third decimal digit rather than rounding). The resulting string-length array (A0 → C8) is:

String Length = [2.01, 2.00, 2.00, 2.00, 1.99, 1.98, 1.96, 1.93, 1.91, 1.87, 1.84, 1.80, 1.76, 1.70, 1.65, 1.60, 1.54, 1.49, 1.44, 1.37, 1.83, 1.75, 1.66, 1.59, 1.48, 1.40, 1.32, 1.25, 1.19, 1.12, 1.07, 1.01, 0.96, 0.90, 0.86, 0.81, 0.77, 0.73, 0.69, 0.65, 0.62, 0.59, 0.55, 0.52, 0.50, 0.47, 0.45, 0.42, 0.40, 0.38, 0.36, 0.34, 0.32, 0.30, 0.29, 0.27, 0.26, 0.24, 0.23, 0.22, 0.21, 0.20, 0.19, 0.18, 0.17, 0.16, 0.15, 0.14, 0.13, 0.13, 0.12, 0.11, 0.11, 0.10, 0.10, 0.09, 0.09, 0.08, 0.08, 0.07, 0.07, 0.06, 0.06, 0.06, 0.05, 0.05, 0.05, 0.04]

Out of these 88 values, 84 (95.5%) are taken directly from the INRIA document. The remaining 4 values were extrapolated using documented patterns and Steinway’s official specifications (for example, C8 ≈ 0.049 m).

Note: you can access per-note editing only in Pianoteq Pro, but even then the software’s allowed string-length range (0.80–10.00 m) prevents you from entering the true Steinway treble lengths. In short, Pianoteq’s UI is not designed to accept the realistic, very-short string lengths found on concert grands like the Steinway D.

Reference: Juliette Chabassier & Marc Duruflé, Physical parameters for piano modeling, INRIA Technical Report RT-0425 (2012). ⟨hal-00688679v2⟩ https://inria.hal.science/hal-00688679v2

Lemuel, Yves is correct in pointing out that the String Length control actually changes the overall length of the piano. Under the hood, all strings do have their proper length and inharmonicity, and these are carefully taken into account when Pianoteq computes the tuning.

You may be interested in the options under "Advanced Tuning > Stretch > Edit stretch points" and "Advanced Tuning > Stretch > Transfer the stretching into Detune note-edit". This will let you see how Pianoteq selects the appropriate tuning depending on the inharmonicity.

Thank you, Alexis. I would like to take this opportunity to suggest an improvement to certain tabs in ‘note edit’.
1-The actual lengths of each string in ‘string length’ so that you can make your own piano plan.
2-he actual tuning frequency of each string in ‘detune’ (frequency or +-cents), which would allow you to clearly visualise the actual stretching. Pianoteq could become a great tool for learning how to tune a piano.
Perhaps in V10...

Translated with DeepL.com (free version)

You may be interested in the options under "Advanced Tuning > Stretch > Edit stretch points" and "Advanced Tuning > Stretch > Transfer the stretching into Detune note-edit". This will let you see how Pianoteq selects the appropriate tuning depending on the inharmonicity.

I tested pianoteq output with a tuner and I confirm the default tuning is yet stretching like on an acoustic piano. From -20 cents to +30 cents on the steinway D.

The value "string length" in pianoteq is the length of the piano, not the length of the strings. The 70cm difference is not pertinent, Pianoteq takes this into account.

Your research is interesting to understand but I think Pianoteq knows very well this theory and is based on this theory.

I tested Pianoteq output as well, and the results need to be examined more carefully. First, the tuner you used matters significantly. Standard chromatic tuners do not have the precision required for this type of measurement. You need a strobe tuner to get accurate readings at the cent and sub-cent level.

Free option: LockOn by SubMission Audio (VST3, requires iLok account): https://www.submissionaudio.com/products/lockon

Paid options: StroboSoft 2.0 by Peterson Tuners (https://www.petersontuners.com/products/strobosoft/) or Polytune by TC Electronic (https://www.tcelectronic.com/product.ht...e=0815-AAG)

Now let us examine the numbers. You measured -20 to +30 cents, totaling 50 cents of stretch. Here is the documented data for actual Steinway Model D pianos:

Piano Stretch Tuning Comparison

Your Pianoteq measurement
Bass (A0): -20 cents | Treble (C8): +30 cents | Total Stretch: 50 cents

Railsback empirical (1938)
Bass (A0): -17 cents | Treble (C8): +40 cents | Total Stretch: 57 cents

Precision Strobe measured Steinway D
Bass (A0): -17 cents | Treble (C8): +40 cents | Total Stretch: 57 cents

Physics-based (Fletcher + 2022 JASA)
Bass (A0): -19 cents | Treble (C8): +45 cents | Total Stretch: 64 cents

Railsback curve data for Steinway D goes from -17 cents at A0 to +40 cents at C8. Not -20 to +30. The Precision Strobe database confirms this with actual measured Steinway D data: http://www.precisionstrobe.com/apps/str...teind.html

Your measurement shows +30 cents at the treble extreme. The documented research consistently shows +40 to +45 cents in that register. That is a 10 to 15 cent discrepancy in the upper octaves.

Regarding the string length parameter: the problem is evident if you use the default stock preset "NY Steinway Model D" in Pianoteq 9.1, which Modartt describes as their most accurate model of the acoustic piano. If you have the Stage or Standard version, you cannot see the individual string parameters. But in the Pro version, you can verify this directly: by default, every string comes with a value of 2.70 m. All 88 keys. Same value.

On a real Steinway Model D, the longest bass string (A0) is approximately 201 cm (79.25 inches). The shortest treble string (C8) is approximately 5 cm. The inharmonicity coefficient B is inversely proportional to the square of string length. If all strings share the same length value in the model, the inharmonicity curve cannot accurately represent a real Steinway D.

From the Pianoteq 9.1.0 Manual, Section 8.1.2 String Length:

"Each piano note produces a complex sound, mainly composed of overtones with approximate frequencies f, 2f, 3f... where f denotes the fundamental frequency. A parameter which greatly affects the timbre (and the tuning) is the so-called inharmonicity: the more inharmonic the strings, the more the overtone frequencies of each string are driven away from their theoretical values f, 2f, 3f... and the more the piano sound will resemble a bell. Inharmonicity decreases very rapidly with string length. Experiment by changing the String length. The difference will be most evident in the bass range. You can choose up to a 10 meter long piano! At such a size, there is almost no inharmonicity. People say that piano manufacturers dreamed of producing pianos without inharmonicity..."

Modartt clearly understands the theory. The manual states it directly. The question is whether the default preset implements that theory with correct per-string values. The evidence suggests it does not.

If you want to verify, open the Pro version, load the default "NY Steinway Model D" preset, and check the string length values across all 88 keys. Then compare what you see to the physics formula:

B = (π³ × E × d⁴) / (64 × T × L²)

Where L is the string length. If L is constant across all keys in the model, B cannot follow the correct curve, and neither can the resulting stretch tuning.

I will continue researching this and provide more precise results with exact calculations. In the meantime, get a strobe tuner and measure again. The data will speak for itself.

The value "string length" in pianoteq is the length of the piano, not the length of the strings. The 70cm difference is not pertinent, Pianoteq takes this into account.

Your research is interesting to understand but I think Pianoteq knows very well this theory and is based on this theory.