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Topic: ajustement microtonal précis (Read 417 times) |
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lenaig29
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Bonjour,
Dans l'idée de créer un tempérament mésotonique, j'ai créé une loi par laquelle des ajustements en cents sont fait sur chaque note (utilisation de l'effet comma). J'utilise un chanteur virtuel dans lequel le vibrato est mis à zéro pour avoir un son le moins vibrant possible. J'ai ensuite vérifié, à l'aide d'un accordeur professionnel prêté par un ami, les décalages effectifs sur la sortie numérique : le résultat n'est pas vraiment satisfaisant, par exemple sur le fa#, que j'indique un ajustement de -11 ou de -7, le résultat effectif est -11.9 (ce qui est trop par rapport à l'écart attendu de -10.3) ; si je passe l'ajustement à -5 le résultat effectif change, mais beaucoup trop!
Bizarrement, un ajustement positif de 11 ou de 10 sur le do bécarre a lui l'effet attendu: résultat effectif 11.6 dans un cas, 10.7 dans l'autre.
Il y a en fait deux problèmes : d'une part un ajustement en valeurs entières de cents n'est pas suffisant pour obtenir une tempérament de manière précise (un écart d'un cent est harmoniquement perceptible, particulièrement quand on veut obtenir certains intervalles purs comme dans le mésotonique), d'autre part cet ajustement en valeurs entières ne fonctionne pas ou en tout cas pas pour toutes les notes...
Quelqu'un aurait-il une solution?
Pour mémoire les décalages usuels en cents (par rapport à l'égal) retenus pour le mésotonique 1/4 de comma sont (de do à si):
10.3, -13.7, 3.4, 20.5, -3.4, 13.7, -10.3, 6.8, -17.1, 0, 17.1, -6.8 (source livre d'Asselin, on trouve de légères différences ailleurs - ici la quinte du loup est entre sol# et ré#)
Bonne fin de journée,
Hélène
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| « Last Edit: Nov 8th, 2019, 4:23pm by lenaig29 » |
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Tony Deff
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Re: ajustement microtonal précis
« Reply #1 on: Nov 9th, 2019, 11:43am » |
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Je regrette d'avoir besoin d'aide pour traduire cela en Français techniques 
These results are symptomatic of measurement tolerance.
Accurate frequency measurement is a problem, and you are assuming an accuracy of 0.1 cent.
This is 1/12000 of an octave, a change of 1 part in more than 17 thousand (1 + 1/17312 ) 12000 = 2 (an octave) 
This can only be done under somewhat impractical conditions - a long "gate" (sample) time and a steady waveform of high frequency (pitch), with no variation of amplitude or harmonics.
The difficulty is that we cannot count fractions of a waveform cycle. The lower the pitch of the note you are measuring, and the shorter the measurement time, the more inaccurate is the measurement.
If you stand at the roadside and count cars, how many pass you in ten seconds - 7.3 ?
Frequency meters can be set to a sample time of 10 seconds, but people are too impatient to wait ten seconds for a change in the result displayed, and for your level of accuracy you need a much longer sample time.
I would trust the calculation more than the measurement.
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An expert is one who knows more and more about less and less until he knows absolutely everything about nothing.
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lenaig29
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Re: ajustement microtonal précis
« Reply #2 on: Nov 9th, 2019, 6:13pm » |
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Thank you for your answer. And sorry for my bad English...
I do not absolutely require that the result should be precise by 0.1 cent, but at least it should be less than 1 cent. I trust more the professionnal ear of a piano/harpsichord tuner (I mean a person, I'm not sure the term is correct in English) who definitely says that the thirds, that should be pure in the temperament, are not. The measurement confirm that.
For the measurement I let the sound more than 10 seconds (I changed the tempo in the myr file). I used a professionnal measurement device.
If I have an adjustement cent by cent which is (theoritically) the case now in the microtonal adjustement, its is ok for one note but not for the entire scale since it can result, depending on the intervals, of more than one cent difference. At least, a possibility of a step of 0.5 cent should be available.
I said theoritically, because the first part of the problem is that sometimes nothing change (example of the F#) even with a difference in the adjustment of 5 cents (the result in the measurement for F# with a microtonal adjustement of -11 cents or -6 cents was exactly the same, around -12 cents). A change appears if I adjust to -5 cents, but then it is far too high...
I would already be relatively happy if the 1 cent adjustement would do what it is supposed to do...
I know this is not a very common problem for Harmony Assistant users, so I do not really expect a solution, but just in case someone had faced and solved the problem...
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Tony Deff
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on Nov 8th, 2019, 4:21pm, lenaig29 wrote:To create a Mean-Tone Temperament (Wikipedia), I created rules by which adjustments in cents are made on each note (using the comma effect).
Using Virtual Singer (with zero vibrato), I then checked, with the help of a professional tuner lent by a friend, the actual shifts on the digital output: the result is not really satisfactory ...
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I still maintain that the result heard is better than the result measured!
Ensuring that your notes are played slowly does not improve the measurement accuracy if the tuning instrument is sampling the frequency every second!
(What is the name and model of this tuning instrument?)
I have always intended - but never found the time - to experiment with different tunings, so was surprised to find that the tuning scale you are trying to achieve already exists!
(This is termed "re-inventing the wheel") 
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An expert is one who knows more and more about less and less until he knows absolutely everything about nothing.
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lenaig29
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Re: ajustement microtonal précis
« Reply #4 on: Nov 14th, 2019, 5:55pm » |
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Hello,
I began with the already existing meantone adjustment but afterwards I had to change it a bit since it does not correspond to what I want : the adjustements are not correct if you want the wolf to be between Eb and G# as is usual, plus I did not want the adjustment to change according the tonality used, which is the case in the already implemented meantone (it can be useful too, but I want it to act as a fixed keyboard). Plus if I remember well, one of the adjustement is not correct anyway (just for one note).
The tuning instrument is Jahn TLA CTS-5-C (really a professionnal tuner…)
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Tony Deff
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Re: ajustement microtonal précis
« Reply #5 on: Nov 15th, 2019, 2:14pm » |
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Thank you for this information, Hélène
I had no idea where the "wolf" was hiding, nor that this noisy wild animal changed position with a change of key-signature.
I shall study micro-tuning further. (I have also found a tuning correction that I disagree with, in the Barbershop/Just scale)
The sales literature for the tuner you are using does indeed claim an accuracy of 0.1 cent - I am still reluctant to believe it!
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Anglophone, HA 64 Win.10.
An expert is one who knows more and more about less and less until he knows absolutely everything about nothing.
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lenaig29
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Re: ajustement microtonal précis
« Reply #6 on: Nov 16th, 2019, 11:18am » |
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Hello,
I would also not say that it is 0.1 cent accurate ; the indication of the tuner (lights) remains the same let's say in an interval of 0.5 cents.
If you are interested in temperaments, here (page106) you can find many temperaments with their shifts in cents:
https://www.veritune.com/download/iOS-User-Guide-7-24-18.pdf
The shifts in this file are given with 0.01 accuracy which is a nonsense in practice, but they are the correct theoritical shifts (at least, I checked for some temperaments and found the same shifts). Usually in the literature the shifts are given with 0.1 accuracy (a 0.5 accuracy would be sufficient I think)
Hélène
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mesotonique_ex.myr