Wood Science Meets Historical Instrument Making

Volker Haag / Eric Kleinmann

Synopsis: What are the differences between how a harp maker and a wood scientist examine the Barberini Harp? This conversation between the harp maker Eric Kleinmann and wood scientist Volker Haag is a commentary on their respective contributions on these pages: Practical Examination of the Barberini Harp and The Barberini Harp Wood Species: The Biology of Sound. Kleinmann builds interpretations of this Baroque instrument, which he believes sound very similar to how he imagines the Barberini Harp might have sounded. In order to build a harp based on a historical instrument, Kleinmann needs to consider various issues, not least that of which wood species to use. In 2016, Harfenlabor asked Kleinmann to investigate the Barberini Harp in more detail and to build a model of a section of the harp in order to test the stringing, and to present his findings at the Convening. One of the conclusions Kleinmann reached is that the column of the harp could not have been made out of walnut. In 2018, Harfenlabor asked the Thünen-Institut to identify the wood species used to build the Barberini Harp. In December 2018, Volker Haag and Valentina Zemke of the Thünen-Institut’s Institut für Holzforschung travelled to Roma with non-invasive 3D-reflected light microscopy and other wood scientists’ equipment. Following macroscopic and microscoping investigations and analysis, Haag and his collaborators concluded without a doubt that the column and the neck of the Barberini Harp were made in walnut. Kleinmann expresses his surprises at this, but explains his reasoning as a harp maker. As part of the 2016 examinations, Harfenlabor also asked harpist and photographer Jakob zur Horst-Meyer to take images of the inside of the harp’s soundbox. These images show a hollowing out of the neck and the area leading up to it. Both Haag and Kleinmann note that this hollowing out was done rather crudely, in stark contrast with the finely finished surface work on the harp. Puzzled by this incongruence, Haag is happy to hear Kleinmann’s explanation, suggesting that this was done in order to pull the strings through this area, probably as part of changes to the pitch of the Barberini Harp.


A commentary on Practical Examination of the Barberini Harp and The Barberini Harp Wood Species: The Biology of Sound
DOI: 10.5281/zenodo.7763054

This Zoom conversation between wood scientist Volker Haag (Hamburg) and harp maker Eric Kleinmann (Rangendingen) is as much of a comment on Kleinmann’s conclusion presented in Practical Examination of the Barberini Harp as it is on Haag’s interview The Biology of Sound—a continued conversation between the two disciplines involved in the construction of historical instruments. His experience as a harp maker informed Kleinmann’s conclusion that the column of the Barberini Harp was not made of walnut, and yet, the wood science proved him wrong. The way in which the harp maker came to this conclusion was illuminating for Haag, the wood scientist. In turn, as both Haag’s examination and the photographs of the inside of the harp made by Jakob zur Horst Meyer in 2016, during the Harfenlabor-commissioned examinations of the harp, discovered that the Barberini Harp’s neck has been hollowed out at some point, it fell to an experienced harp maker such as Kleinmann to provide the likely explanation for this change.

© Harfenlabor 2022
Licensed under CC BY-NC International 4.0

Translated transcript of the conversation:

Volker Haag: [00:00:12] Just like me, you’ve seen the Barberini Harp up close. You have engaged with elementary construction. People like us, who have spent time in instrument making and artisanal crafts, work with a relatively high degree of precision, and to put it simply, try to make everything really “beautiful.” When you look at the Barberini Harp now, what you see is completely unique, an incredible visual attraction. But when you look inside the harp, when you look at the parts leading into the neck, you ask yourself if the side walls have been worked on with an axe or how, and I had a similar feeling when I looked inside the harp. I would like to know how you feel about the fact that it is all show and no substance?

Eric Kleinmann: Yes. I have to say that the surface work on the Barberini Harp was done by people who only worked surfaces. Gilding is not just applying a bit of oil and then applying gold. Oil gilding has a chalk base formed by a mix of Bolognese chalk and animal glue. That’s why you cannot get through it [with anything]. It’s not a thick coat of lacquer, but like a very hard plaster that you have to scrape out in fine detail afterwards so you can see the fine lines again, you have to imagine it’s like a thick liquid curd yogurt. I’ve done this myself, too. So, the surface was probably made by a decorator and a gilder. Harp making is pragmatic work: you avoid elaborate work that also costs money.

Haag: Of course, that is also an aspect, yes.

Kleinmann: [00:02:30] Well, I’ve looked at different harps. Some of them were made excellently and seeing some of them I thought, “Oh. I could have done this as a 16-year-old, had I wanted to.” You know what I mean? I was also astonished. I found some details interesting, which I use in my work too. They also worked inside the harp; this is not the first soundboard. I think the soundboard is not original. Of course, you can rummage around in the instrument and make something. Actually, I found the inside to be not so tragic.

Haag: Did you have the impression that this part, the neck of the harp, was basically always hollowed out? Because, if I understood you correctly, there’s been reworking over the years. What did you notice? “Oh, that could not have been from the beginning.” Did you notice this immediately? Or was it a process during which you realised, “No, that must have been done later.”

Kleinmann: [00:03:50] I realised relatively quickly it had been done later, because it was not, as you said, done cleanly. If the neck had been separated from the column, it could have been done cleanly. You could have turned the neck around, fixed it to the table and worked it from above. It was done the way I explained in the [Convening] talk: hollowed out from below with irons. That’s what they did with some harps later on. On the left and right they had a part of the neck closed on the top like a bridge. It was not their aim to make the instrument lighter. I think they tried to bring the strings down through the middle. If the neck had been made in two parts, they would have pierced the column and inserted the string into the hole from the bottom or from the top.

Haag: I see.

Kleinmann: There are such harps in Paraguay, for example, modern harps. Enthusiasts also made harps with strings inserted through the middle. Those have the same problem as this harp, namely that the lowest string hits against the decoration at the base, presumably for construction reasons. I interpret this as an error in planning. Or they simply wanted to add more strings later. That happened with many harps. Over the course of time people said, “We might need a G down there, let’s make another string hole there.” The interesting thing about the Barberini Harp soundboard is that the last string hole, on this square inserted into the soundboard, about a millimetre thick and made of hardwood, has no crack in the middle from ageing and stress. All the others have a crack in the middle. This string has probably not been used much or not at all. That is, for me, an indication of this. So, there was a problem up there somewhere, which is probably why they tried to pull the string through the middle of the neck.

Haag: [00:06:34] Yes, yes, crazy. And on top of that, of course, that the instruments, guitar, for example, were still developing and evolving until the 1920s. This also goes for the harps, at least as in that their development wasn’t finished 400 years ago. And one, basically, couldn’t know what trends would come 100 or 200 years later—which is now 200 years ago for us.

Kleinmann: This is how I can best explain this to you: I am making a Barberini Harp here, but this is not a copy.

Haag: Yes.

Kleinmann: I didn’t have all the measurements at the time. In terms of construction, this harp is the same; I have the braces over the top like on the Barberini Harp, which I will come back to. I made everything as on the Barberini, it is just that the measurements are not exactly the same. Moreover, the Barberini Harp originally had C3 as the last string. Today, when you sell an Italian harp, the musician also wants to play Händel on it. The typical Händel… [such as the Harp Concerto in B Flat Major, Op 4, No 6, HWV 294].

Haag: [00:07:51] Something I don’t know much about.

Kleinmann: To do this, you need a D3 and an E at the top.

Haag: And you can see that in the construction.

Kleinmann: [00:08:01] That’s what I do. That’s why the body is also a bit longer in my case, so there’s room for it.

Haag: Ah, OK, so, basically, a modern interpretation of the Barberini Harp.

Kleinmann: [00:08:12] Yes, yes. I’ve never claimed it’s a copy of the Barberini Harp, it is in the style of the Barberini Harp, with similar dimensions. There is hardly any difference in sound, I think.

Haag: And what kind of wood do you make them out of?

Kleinmann: [00:08:26] Now, we come to this. I thought it was really interesting how you found out what [wood] it is from the photos and surfaces. I’ve got to say, I know a lot about dendrochronology because I live in a house built in 1655. The house is made of fir. After the Thirty Years War, there wasn’t much oak here and it was really expensive. Fir was available but not spruce; there was no spruce where I live. There was spruce in the higher Alps, possibly in the Schwarzwald. The fir tree was actually native here. The spruce has been considered a modern tree for the past 250 years. It was imported, as quick growing. That’s why it’s fir. I thought it was interesting how you did it. I now realise I have been wearing blinkers in relation to what wood an instrument is made of, because I already know what I amusing. I would never have used walnut. I can tell you why. You explained the structure. Whether 100 or ten years old, walnut wood swells when you introduce humidity. Every wood does. We have to always be clear about that. I only build large Baroque harps in the winter—this is when wood has the highest density as the environment is dry. When the instrument is finished, it must be immediately removed, it must no longer remain in the workshop. That would destroy the instrument because the air is simply too dry. But the problem we have today is that with central heating the rooms are always dry, and we’ve got to take this into account. All the wood I take for the frame, what you now call neck and column, is also chamber dried. That way, it doesn’t crack in dry air.

Haag: Yes.

Kleinmann: [00:10:45] I’ve made walnut harps, and it made me really angry, as, for example, on the neck, around the brass reinforcement plate, a two to three-millimetre gap showed after two months.

Haag: That’s a lot.

Kleinmann: Yes. Walnut contracts a lot, and its capillaries are quite coarse, as you know, so moisture gets in there.

Haag: [00:11:17] Yes. Especially too, given its differently sized vessels, since walnut is semi-ring porous.

Kleinmann: And if a piece of wood has not grown straight, there is still tension in it.

Haag: Yes.

Kleinmann: I always have to reckon with these things.

Haag: Yes, that’s what you say, the maple tree, yes. Maple is, basically, a larger tree, and, I assume, an old tree. As such, it has a relatively large and more homogeneous area. Walnut trees of that size are extremely rare.

Kleinmann: And would not have grown straight.

Haag: And would not have grown straight. I did my master craftsman’s degree in carpentry 15 years ago and decided to build my masterpiece out of walnut. And I cursed it so much, because I had to buy more wood all the time. Every time I cut something open, there was something stuck in it. I didn’t make it easy for myself. But I am more than 100 per cent sure that [the Barberini column] is walnut. You could see it very clearly afterwards.

Kleinmann: [00:12:31] On the front, where you can see the wood amidst the black decoration, you can also see that the wood is relatively rough and raw. I would have bet it was Robinia, you have a lot of them in Italy. It is extremely tough and stable, but not good for carving because it is brittle.

Haag: As far as I know, the oldest Robinia we have in Europe hails from its namesake, the French court gardener Jean Robin, from around 1600, I think.

Kleinmann: Ah, okay, okay.

Haag: [00:13:20] Robinia trees come from North America. The oldest Robinias we have in Europe were planted by Jean Robin, as a wood gardener, along the Seine in Paris. That means that at that time there wouldn’t have been any Robinia wood in Europe unless imported from North America.

Kleinmann:Another wood, besides walnut, that has a similarly coarse structure is sweet chestnut, that’s what I also had in mind.

Haag: Oh, yes, that’s the one. Yeah.

Kleinmann: I have a Romanesque harp with the body made of two half-shells of sweet chestnut. It is also tough, but quite brittle too. So, it’s not good for carving.

Haag: Yes, true.

Kleinmann: And walnut is more homogeneous. It also leans in the direction of pear, so that when working it, it does not split so fast, it is easier to carve it. But I thought, “Walnut? It can’t be.” I make my [harps] in maple.

Haag: [00:14:28] So, you mean now that it can’t be walnut because it would have been too difficult to realise?

Kleinmann: But yes, we must always consider that the Barberini Harp was built at a time when they had just invented them.

Haag: Harps of this type?

Kleinmann: Of this size. They have only existed since 1620 or so. That is, people didn’t have much experience [in making such harps] at the time either.

Haag: Exactly, this speaks of the experimental phase, as I said at the beginning. Such an instrument had never existed, they had no history of developing such harps.

Kleinmann: But I think, because the body is made of eleven parts, it’s quite a lot and elaborate to make.

Haag: Yes, yes.

Kleinmann: We now come to the body. I filmed inside it with a special camera.

Haag: Yes, I tried that too with a telescopic probe. Exactly.

Kleinmann: [00:15:30] And it worked really well. At the bottom, I could put the camera through the sound hole chewed on by mice. I used a 360-degree camera to take the photos.

Haag: Yes. And what do you say about the wood for the body?

Kleinmann: Well, as the inside is not so parallel, I thought, well, OK, this would have been either pine or cypress wood.

Haag: Yes, right.

Kleinmann: I know fir has narrower annual rings. And I would never have guessed that the soundboard was fir. Today, they actually make such soundboards in spruce, grown far up in the mountains. I buy mine in Switzerland, grown at an altitude of over 1000 metres. The annual rings are very even and bring the needed sound quality.

Haag: [00:16:28] I think it also has something to do with this development phase, when fir was used a lot. For example, it was used in the construction of larger stringed instruments such as the cello or the double bass, in which I have often been able to identify fir wood. As preparation, we examined an Erat Harp in the Deutsches Museum in München to test our equipment. And the soundboard was actually made of spruce. You can differentiate very well with very fine structural features, as we call them. The wood rays were characteristically high and wide, and there also were prismatic crystals, which are typical for fir. The softwoods are more difficult to differentiate than hardwoods. There are quite a few structural features.

Kleinmann: I also find that fir, when a little older, has less difference in colour between the hard and soft annual rings. The difference is not as visible as with spruce, where the difference between hard annual rings, which are darker, and the in-between, which is lighter, is greater than with fir. That is just what I see. I have also worked with fir here.

Haag: Yes, yes, I was just going to say that each has their own characteristics, depending on whether one approaches it macroscopically or microscopically.

Kleinmann: [00:18:05] I also have my own four walls in the forest with fir and spruce.

Haag: You would know, living in a fir house.

Kleinmann: Sure, I’ve dealt with it, sure. I found it totally exciting and interesting. So, it was also clear to me that in macrobiotic area you can see that well. The problem is, of course, that we’re not allowed to remove anything from the harp. I also tried to get permission to take samples. I could’ve taken them without being noticed. But you don’t do that.

Haag: No, no, no.

Kleinmann: You don’t do it. But you could have taken other samples and it was good that you did it that way.

Haag: [00:18:51] I had two options. I informed Mrs. [Sandra] Suatoni, the director, and told her that, based on the examination possibilities I had on site, I can conclude that it’s fir wood. But how much precision did she need? I said I couldn’t bet my life on it. But I showed her—of course, I am very skilled at this—how I removed a tiny, tiny, piece of pine wood I had with me to show I could remove such a piece very carefully. She couldn’t believe how tiny it was, and was then all right with us taking a tiny fragment from the hole where the mice had chewed at it.

Kleinmann: You did that. Yeah, sure. Yes, so I would have, so I would have. I suggested to do it in another spot, where not even an expert could see it anyway. From this hollowed section, for example, in which so many splinters stick out, one would be able to easily take one with tweezers.

Haag: [00:19:55] Another team went before us and took X-rays [of the Barberini Harp], and they had the permission to take a sample. I wrote to them and asked whether anything was left over from this sample for scanning electron microscopy examination. They sent it to me, and in the mean time we went further, but that hasn’t been published yet. We also had the fragments examined in the USA, confirming it was walnut wood.

Kleinmann: Uh, sure, yes, but that’s actually … not common. Nowadays, most harp makers use maple for the frame, the neck and the column.

Haag: [00:20:49] Yes, I know that from Torres, the guitar maker. And then there are these French Macaferri guitars, jazz guitars, and they also like to use walnut. Of course, as a lot less wood is processed, fewer surfaces are used, it’s possible to use walnut for guitars.

Kleinmann: I found it quite surprising this is walnut. I explained in my lecture that you can clearly see that this was done afterwards. You can see from the insertion of the tools that they only came in at an angle because the decoration at the bottom interfered.

Haag: Yes, sure.

Kleinmann: That has nothing to do with making it easy. Well, that’s rubbish. They were just experimenting. They had to. And you can clearly see that the ornamentation on the top could also be removed. It was removed. They did a lot of experimenting up there, which was later rather detrimental to the statics. To what you said about the frame: it doesn’t have to be made in tone wood. Of course, maple is a good tone wood, but the frame contributes nothing to the sound.

Haag: [00:22:20] Yes, it has to be a very sturdy wood.

Kleinmann: It has to be sturdy wood. I’d like to tell you what it’s like when I saw for a column. I brought you something. You can easily recognise a cross-section through the trunk.

Haag: And standing annual rings.

Kleinmann: I need the annual rings. And from the trunk area… you know that it has a north, west and an east side.

Haag: Ah yes, naturally.

Kleinmann: People prefer to take the west side, where the tree grows more slowly as it’s more exposed to the wind. Looking at a laid-down trunk, you can see where the west is in Central Europe. The middle is not in the middle, it’s shifted and that’s where I take the column out.

Haag: Yes, exactly, great. Likewise, for a guitar neck: it must be standing annual rings.

Kleinmann: [00:23:20] But now the column is two metres long. I have an uncarved column; the column that stands there is now 5.5 by 5.5. It was cut into 7 by 7 from the plank and it stood there for a year. By then it’s no longer straight, so I mark the direction it bends in and then make it 6 by 6. Of course, it has a bit more at the top, it is a bit wider for the transition to the neck. In principle, I have to draw it in so that I know where the tension is in the wood, because there is always tension in the wood. It will not be released; it can’t always be released. You know, when this is like this and the fibre is straight, there is tension inside…

Haag: Naturally.

Kleinmann:… that remains. And if you take something out of it, the tension and the structure in the wood changes. Therefore, if you now saw a 7 by 7 plank and put it up until it settles and then you can continue working. It’s important that I know where the tension is in the wood because it has to work against the string tension. In a two-metre-tall column, you have to work with that.

Haag: [00:24:48] Eric, with an eye on the time, perhaps one last question. What do you think, when was the last time the Barberini Harp was played?

Kleinmann: It’s hard to say. I’d say it was more than two hundred years ago, I guess. Or a hundred. What was experimented with there was done later, probably at the time when the other holes were drilled.

Haag: Yes.

Kleinmann: By the way, the same applies to the neck. You have to take a board that is already bending when you saw it out of the plank. On the top of the harp top you have the pin and the string going down. The neck must have tension against the string. Even if it’s straight, the tension in the wood remains and is naturally more tension-resistant if there is tension in the wood. That’s what you have to take into account with this big harp. The instrument is already quite warped; I saw where they filled the gaps. So, it was not straight, it does not really stand straight. It might also be interesting for you to know that at the back of the harp it is not the body producing the sound: the “space” produces the sound. The soundboard and the strings are the most important for the sound. Modern harps have a body made of cardboard; I almost fell over when I heard how good they sound.

Haag: [00:26:39] Ah okay, there is an experimental guitar by the great Antonio de Torres. He actually once built a guitar with a body made of cardboard. Out of cardboard. Yes, super.

Kleinmann: Well, I found most interesting how you found that out. The wood is… as I said, I am, of course, blind to some things as an expert in the construction of such harps, as I always start from what I do practically. And then, of course, I’m also “business” blind and don’t think the same way. So, walnut. I would never have taken it to be walnut.

Haag: Yes, equally, I found that incredibly interesting. How you were able to interpret the construction and determine when, where, what and above all for what reason changes were made. I have also learnt a great deal in the process.

Cite:&&Volker Haag and Eric Kleinmann, <i>Wood Science Meets Historical Instrument Making</i>, Barberini Harp Project / Interviews, by Harfenlabor, May 2, 2022,, Zoom recording, 27:52,