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Re: CHAS for Dummies [Re: pinkfloydhomer] #2195531
12/10/13 12:12 PM
12/10/13 12:12 PM
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Phil D Offline
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CHAS is an equation that describes a well-stretched piano using the balance between a stretched 15th and a narrow 12th. This is what many of us habitually try to tune anyway. It has merit in the way the equation allows you to see what happens to the beatrates of other intervals if this stretch is maintained consistently - specifically the way the 5ths and 4ths behave. If I remember correctly, the fifths reach a minimum beatrate close to pure somewhere below the temperament region (depending on the scaling) and get progressively narrower as you move upwards and downwards from that minimum. This is the consequence of semitones being the size that they are supposed to be in this system. It also has progressive 4ths.

Alfredo's tuning technique attempts to incorporate these progressions into the tuning, but the accuracy required is very high, with diminishing returns.

There's no denying that this size stretch results in a beautiful tuning. But there's a massive disconnect between the theory (which is actually very simple, it just suffers from a lot of obfuscation and bad communication) and the practice, and unfortunately that gap has been filled with alfredo's own tuning philosophy. (I'm not saying your tuning technique is bad, alfredo, it's just separate from the model you have presented, yet you treat it as the same. Slow-pull technique and pin 'charging' is nothing to do with CHAS)

There's also space within his maths for other 'delta' values, amounting to different stretch patterns. I find it an adequate model for a theoretical 'good' tuning on a theoretical piano. I believe if it was programmed into a dedicated ETD then it would produce good results similar to StopperStimmung.

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Re: CHAS for Dummies [Re: Phil D] #2195540
12/10/13 12:37 PM
12/10/13 12:37 PM
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Originally Posted by Phil D
CHAS is an equation that describes a well-stretched piano using the balance between a stretched 15th and a narrow 12th. This is what many of us habitually try to tune anyway. It has merit in the way the equation allows you to see what happens to the beatrates of other intervals if this stretch is maintained consistently - specifically the way the 5ths and 4ths behave. If I remember correctly, the fifths reach a minimum beatrate close to pure somewhere below the temperament region (depending on the scaling) and get progressively narrower as you move upwards and downwards from that minimum.

Not so. Are intervals remain the same size everywhere in chas as chas doesn't take inharmonicity into account at all, hence it has no relevance to piano tuning.

Kees

Re: CHAS for Dummies [Re: Phil D] #2195544
12/10/13 12:41 PM
12/10/13 12:41 PM
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Originally Posted by Phil D
It has merit in the way the equation allows you to see what happens to the beatrates of other intervals if this stretch is maintained consistently - specifically the way the 5ths and 4ths behave.


Hey Phil, how do you see this?


www.tunewerk.com

Unity of tone through applied research.
Re: CHAS for Dummies [Re: pinkfloydhomer] #2195548
12/10/13 12:50 PM
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It's not in the original paper, Tunewerk, but it came up in the discussions, so it'll be buried somewhere in the many threads. The derivation would be tedious but you can see how it might be done.

Inharmonicity is not taken into account in the equation, Kees, but he compares his values to the railsback curve, which is an idealised inharmonicity model of a piano, and it compares favourably.

As I said, an idealised model for an idealised piano.

Re: CHAS for Dummies [Re: Phil D] #2195554
12/10/13 01:06 PM
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Thanks for the reply, Phil.

No, I don't see how this could be done. Reversal of 5ths and 4ths was an inharmonicity artifact first discovered by Fairchild. No math will predict or model this, unless you are talking about finite element analysis of soundboard loading and scales.

CHAS too easily becomes a Shopsmith talisman for answering everything piano. I think this is a problem that leads to its discredit.


www.tunewerk.com

Unity of tone through applied research.
Re: CHAS for Dummies [Re: Phil D] #2195555
12/10/13 01:08 PM
12/10/13 01:08 PM
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Originally Posted by Phil D

Inharmonicity is not taken into account in the equation, Kees, but he compares his values to the railsback curve, which is an idealised inharmonicity model of a piano, and it compares favourably.

He just states that it compares favourably, without ever showing the CHAS and Railsback curves together. The CHAS "curve" which is supposed to be like the Railsback curve is actually just a straight line. It does not "compare favourably" at all.

Kees

Re: CHAS for Dummies [Re: pinkfloydhomer] #2195713
12/10/13 06:31 PM
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I've never understood how 4ths and 5ths "reverse". When and where on the keyboard does this supposedly occur? Aren't all 5ths supposed to be narrow and all 4ths wide, no matter the register?

Re: CHAS for Dummies [Re: pinkfloydhomer] #2195744
12/10/13 07:24 PM
12/10/13 07:24 PM
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Well I just took his word for it really, so I'm happy to be corrected.

erichlof, it wasn't that the 5ths become wide, it was that the fifths become less narrow, and then more narrow. So the direction of the change of narrowness reverses.

Re: CHAS for Dummies [Re: erichlof] #2195748
12/10/13 07:34 PM
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Good question, Erichlof. This is something I'd really have to pull out the data for, which I don't have around at the moment.

To the best of my memory, increased soundboard loading causes negative inharmonicity on 3rd partial of most pianos, around the 5th-6th octave. This causes the 5th to be pure with less stretch and, at the same time, the 4th to be pure with more stretch (neg. iH acting on both sides of these complimentary intervals).

Very rarely is there a crossover. It has been documented and is possible with extreme negative iH, but it is rare.

The real world outcome of this effect is you'll notice it is easier to get both 4ths and 5ths pure as you rise out of the temperament region.

This is an excellent point to post here, because tuning models never represent variable partial fields on a real piano. When partial fields fluctuate, the rules of tuning fluctuate.

Phil - glad to hear, and to know that all together we can clear up misinformation! smile

Last edited by Tunewerk; 12/10/13 07:43 PM.

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Re: CHAS for Dummies [Re: pinkfloydhomer] #2195761
12/10/13 08:07 PM
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Ahh... thank you Phil and Tunewerk for the explanations. I think I understand a little better now. I guess it's kind of like in physics when you can have negative acceleration. smile This concept always tripped me up in High School and here I am many years later encountering it again with a completely different system!

Thanks!
-Erich

Re: CHAS for Dummies [Re: pinkfloydhomer] #2195784
12/10/13 09:06 PM
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Many intervals exhibit anomalous behaviour. All aural tuners who use all the test intervals in the whole piano must have noticed them, particularly how single octave size and double octave size change places on several notes in and around the top octave, even in the best pianos..
This is maybe the most readily apparent of them, at least it's the first one I ever noticed as an ardent student of all this. It's only about 30 years ago that I started to choose the single octave to tune to instead of the double octave when the alternatives were too noisy in the smaller intervals. That was the time I started working in more recording studios and spending more time listening to playbacks with other musicians than tuning. (1 hour tuning/3hours listening).

Bass strings exhibit even more random exchanges but that's to be expected even in the largest pianos. Far too random to try to marshal them into some sort of order.

ETD's never pick up on them or pick up on the wrong ones.

A wizened old tuner once told me, don't listen too hard, you'll go crazy. Maybe that's what's happnin'.


Amanda Reckonwith
Concert & Recording tuner-tech, London, England.
"in theory, practice and theory are the same thing. In practice, they're not." - Lawrence P. 'Yogi' Berra.


Re: CHAS for Dummies [Re: pinkfloydhomer] #2196421
12/12/13 05:21 AM
12/12/13 05:21 AM
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Hi,

Posted in the "Sample" thread:

Originally Posted by rxd
Originally Posted by alfredo capurso
Originally Posted by rxd
Originally Posted by bkw58
Does the pianist not have at least something to say about it? It's not like he's poking around on an old Underwood. He takes the best that the tuner can provide with what he has to work with and creates his desire with very specific skills at his finger tips.


I must confess to not listening again, I started to but refused to pick through all the talking but the pianist can do much more than we think.

The sustain varies very subtly from note to note in all pianos. A stage piano doesn't always get the maintenance it should and equality of sustain suffers.
while there are ways of poking through the strings with a long needle to obtain more sustain from the hammer, tuning on the day of a big production like this rarely allows for any refinement.

I have to sincerely question isaacs experience of this kind of work. He claims to know but his comments show a distinct lack of understanding. There's more of self promotion in his nit picking criticism. I would expect sympathy with the situation from a real fellow professional. He sounds to me like a really talented amateur who hangs around the profession and then totally falls apart when the real job has to be done. I've known quite a few.


rxd,

I think that only a boor would direct those words to a technician as Isaac, and I do not see how that style can help to describe our work. I think you ought to apologize.
.


I quite agree and understand fully where you're coming from and the emotional content carried over from other threads. - an all too common occurrence.
Since you raised the issue again, It took a few words in order to address an ongoing problem. A totally unfounded, unnecessary and pretentious criticism of a compressed recording couldn't go unchallenged at the same level.

Am I to assume that you agree with isaacs original "criticism" when he himself posted later an admission that he really couldn't tell the difference between what was the piano and what was the tuning and then delete that post a few hours later?

I suggest you read the complete thread. It's all there and doesn't need the deleted parts to be indefensible.

Constructive criticism-Yes.
Self serving, Ill considered boorish and unfounded carping,- a resounding No.


rxd, when you mention "..the emotional content carried over from other threads..", do you mean this thread? Or is it the "How long should it take?", where you wrote:

Originally Posted by rxd
[/quote]
........ and I think about art.

Best regards, a.c.
.

In all branches of the arts, phrases like this have long been regarded, rightly or wrongly as the last refuge of a charlatan.

I have read some of your work as presented here and experimented with some of it.

You have just another opinion. It is a different twist on an old problem that has been pondered and discussed by generations of fine mainstream tuners who have had to tune the old designs of smaller grands produced by some of the finest makers. Your solution still doesn't address the basic problems.

When I pondered whether or not to dine with you, one of the issues I considered was whether I would be spending a bright convivial evening with a fellow professional or would I be taken hostage by an intense and over enthusiastic amateur. Most people have relationships. Some take others hostage and think it is a relationship.

I asked you directly of your professional experience and you gave me a brief dismissive and evasive answer. I also answered fully to some of your direct technical and artistic questions of me. Your replies to my answers betrayed that you hadn't the feintest idea what I was talking about. It's all in the archives here.

Now you resort to an attempt to insult us all and in the name of art no less.
Ooooooo get you!!.

Let yourself out when you've finished tuning and switch off the lights. We're going to bed.


What I am saying, rxd, is that your insinuations do not help, and in the Sample thread I was not concerned about me, but Isaac.

Sure, I cannot say I am happy to read that I would be a charlatan, or an amateur, or one that would try to take you hostage, or... crazy, as you last wrote in this thread.

Let me suggest: take it easy, be respectful and filter your thoughts and fantasies three times before you post.

About theoretical and practical/technical contents... later on.
.


alfredo
Re: CHAS for Dummies [Re: pinkfloydhomer] #2196424
12/12/13 06:00 AM
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Sorry, everyone, I appear to have picked up another self obsessed stalker in the above post who, not content with insulting us all and being censured for it, has chosen to mix up the content of two different threads for their own ends.

I apologise to you all for any inconvenience or confusion this has caused.


Amanda Reckonwith
Concert & Recording tuner-tech, London, England.
"in theory, practice and theory are the same thing. In practice, they're not." - Lawrence P. 'Yogi' Berra.


Re: CHAS for Dummies [Re: pinkfloydhomer] #2196425
12/12/13 06:27 AM
12/12/13 06:27 AM
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IMO, there is little to be sorry about, when we try to be clearer.

You confirm your attitude again, rxd. BTW, do you have a name and surname?


alfredo
Re: CHAS for Dummies [Re: pinkfloydhomer] #2196428
12/12/13 06:50 AM
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Originally Posted by pinkfloydhomer
I have read the threads about CHAS, and I must admit I don't get it, even if I have a solid mathematical background.

Can someone explain it to me in plain terms? Or at least in mathematically unambiguous terms?

Would it be possible to tune CHAS with TuneLab?


Hi pinkfloydhomer,

Unfortunately I do not know what the user can do with TL, and I am not familiar with recent ETD's; I guess Robert Scott may say, perhaps it is worth a PM?

As for the Chas maths, which is the point you do not get?

Regards, a.c.
.


alfredo
Re: CHAS for Dummies [Re: alfredo capurso] #2196430
12/12/13 07:11 AM
12/12/13 07:11 AM
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Originally Posted by alfredo capurso
IMO, there is little to be sorry about, when we try to be clearer.

You confirm your attitude again, rxd. BTW, do you have a name and surname?


No he does not have a real name. He is a robot from a Boy Scout project that went horribly wrong. rxd is just a model number.


Jeff Deutschle
Part-Time Tuner
Who taught the first chicken how to peck?
Re: CHAS for Dummies [Re: rXd] #2196441
12/12/13 07:46 AM
12/12/13 07:46 AM
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Oh no, he found it..

This thread, even though already resolved, is about to become extremely confusing. And long.

Originally Posted by Alfredo
Let me suggest: take it easy, be respectful and filter your thoughts and fantasies three times before you post.


This is great advice that you should follow yourself, Alfredo.

Originally Posted by Alfredo
About theoretical and practical/technical contents... later on.


It always is later on, even if unsolicited. And when you do explain, you never do really explain.

Yes, I think it is clear to everyone that CHAS is more about your own personal show than presenting something of worth.


www.tunewerk.com

Unity of tone through applied research.
Re: CHAS for Dummies [Re: pinkfloydhomer] #2196450
12/12/13 08:40 AM
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Xd is the original model designation but it all went horribly wrong.
Started to exhibit human traits and developed attitude problems so the R prefix stands for "rebuilt". Now the attitudes are just right.

Some in the piano profession in a few parts of the world know exactly who I am. Some even know who I used to be, still fewer know what I used to be.

Nobody knows why.


Amanda Reckonwith
Concert & Recording tuner-tech, London, England.
"in theory, practice and theory are the same thing. In practice, they're not." - Lawrence P. 'Yogi' Berra.


Re: CHAS for Dummies [Re: rXd] #2196452
12/12/13 08:45 AM
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Originally Posted by rxd
Xd is the original model designation but it all went horribly wrong.
Started to exhibit human traits and developed attitude problems so the R prefix stands for "rebuilt". Now the attitudes are just right.

Some in the piano profession in a few parts of the world know exactly who I am. Some even know who I used to be. still fewer know what I used to be.


And NOBODY, oops, nobody knows what you will become! (Or are you becoming?... naaah)


Jeff Deutschle
Part-Time Tuner
Who taught the first chicken how to peck?
Re: CHAS for Dummies [Re: pinkfloydhomer] #2196454
12/12/13 08:48 AM
12/12/13 08:48 AM
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I am becoming very becoming.

Thanks for a good belly laugh, Jeff

Oh, the original Xd couldn't laugh at itself.


Amanda Reckonwith
Concert & Recording tuner-tech, London, England.
"in theory, practice and theory are the same thing. In practice, they're not." - Lawrence P. 'Yogi' Berra.


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