«The Trombone of Anton Schnitzer the Elder in Verona: A Survey of Its Properties and Their Acoustical Significance Hannes W. Vereecke The growing ...»
The Trombone of Anton Schnitzer the Elder in Verona:
A Survey of Its Properties and Their Acoustical Significance
Hannes W. Vereecke
The growing interest in the performance of Renaissance music for brass instruments
has created an increasing demand for accurate reproductions of period trombones. The
reconstruction of such instruments has raised many questions concerning the effect of
geometrical design, materials used, and processing techniques on tone quality and playing behavior. Performers and audience members, lacking understanding of these parameters and their acoustical effects, are generally unaware of their relevance to historical performance.
There are few primary sources at our disposal that offer information on the manufacturing process, thus one is forced to rely on information that can be obtained only from scientific analysis of surviving instruments.
Approximately half of the surviving sixteenth-century trombones are the work of members of the Schnitzer dynasty of Nuremberg. Of the three instruments attributed to Anton Schnitzer the Elder, the trombone made in 1579 (see Figure 1) represents one of the most important sources for study for scholars of the early trombone.1 Unlike the majority of surviving instruments, the acoustically important parts of this trombone are in original condition, making the instrument particularly suitable for scientific analysis.
Additionally, there are several original documents relating to the instrument, including an official letter of acquisition and numerous inventory entries that allow us to trace its early history.2 Furthermore, some music that may have been played on it survives,3 thereby offering insight into associated musical characteristics, such as tessitura. Finally, a mouthpiece preserved with the instrument is presumed to be from the same period. It is one of only four mouthpieces associated with surviving Renaissance trombones.4 The fact that its cup diameter resembles that of modern mouthpieces makes it particularly interesting for purposes of modern reconstruction and performance.
Figure 1: Trombone by Anton Schnitzer the Elder (Nuremberg, 1579).
Verona, Accademia Filarmonica, catalog no. 13.301. Photo by Maurizio Brenzoni.
26 HISTORIC BRASS SOCIETY JOURNALReferences to this instrument in scholarly literature are generally brief, and few of these mention its physical properties. The catalog of the collection of the Accademia Filarmonica, by John Henry van der Meer and Rainer Weber,5 and an unpublished restoration report by Max and Heinrich Thein6 offer the most detailed information, but even the data provided there falls far short of an in-depth analysis of the instrument.
The main purpose of the study described here was to conduct a comprehensive analysis of the physical properties of the instrument and determine their acoustical significance.
A secondary objective was to investigate its properties for purposes of reproduction and performance. A team consisting of Rainer Egger (Basel), his associates, and the author constructed an exact copy of the instrument and its associated mouthpiece, based on the data derived from the present study. Comparison of the input impedances of the original and our copy reveal that the copy has an acoustical footprint comparable to the original instrument.
The documentation of the physical properties of historical brass instruments poses many challenges. The complex concerns surrounding construction and preservation restrict the use of certain measuring devices, often to the detriment of the accuracy of the results.7 Measuring the bore profile with conventional measuring tools The acoustical properties of resonant air columns depend mainly on the bore profile. When sound and playing characteristics of different instruments are analyzed, geometry plays a dominant role. In compiling bore lists, acousticians apply a rule of thumb that states that a difference of 1% of the total bore diameter will have a measurable acoustical effect. In the case of the present instrument (hereafter indicated by its catalog number, 13.301), the error of measurement should ideally be smaller than 0.1 mm. The cross-section of brasswind instrument tubing, particularly in historical instrument tubes, is not perfectly circular. As a result, it is necessary to measure every diameter on two axes, 0° and 90°, and extract an average value.8 Standard vernier callipers were used to measure the tubing; for the bell profile and mouthpiece, calibrated probes were necessary. The zero point was set at the intersection of two radials placed across the end of the bell, and thereby the distance the probes intruded from that zero point could be measured. Knowing the intrusion of various diameters, a bore list could easily be derived.
Measurement of the wall thickness with an ultrasonic gauge The principle of ultrasonic wall-thickness gauges is based on the measurement of the time of transmission of an ultrasonic impulse. Consequently the thickness of the material may be determined mathematically, based on the velocity of sound traveling through the material being tested. Brass is a copper-zinc alloy, therefore as the amount of zinc increases, the value of the speed of wave propagation decreases.9 The principal advantage of using this method is to be able to gauge thickness without requiring access to both sides of the VEREECKE 27 wall. The main disadvantage is that it cannot be used for inhomogeneous materials such as wood because the speed of propagation is not constant. Rooney and Reid describe in detail the principles of this method and its implementation for the measurement of thin wall tubes.10 The measuring device used in the present research is the CL 5, made by GE Inspection Technologies.11 Material alloy analysis with X-Ray Fluorescence X-Ray Fluorescence (XRF) is a non-destructive method used to investigate the chemical composition of materials. The method is specifically appropriate for the analysis of historical brass alloys, and as such has been used by several researchers for this purpose.
The principle of XRF is based on the excitation of the elements present in the sample by means of primary X-ray radiation. The emitted secondary X-ray radiation is analyzed by an energy-dispersive detector.12 The measuring device used in the present research is the handheld XRF, type Spectro X-Sort made by Ametek-Spectro in Kleve, Germany.
Evaluation of intonation and response with input-impedance measurements A brasswind instrument is an acoustical system whose acoustical properties can be characterized essentially by its input-impedance, the ratio between the pressure and the flow of air at the mouthpiece. An input-impedance curve represents the reaction of the instrument to the energy impulse produced by the player. A peak in the impedance curve Figure 2: Input impedance curve of no. 13.301 (a1=448Hz).
28 HISTORIC BRASS SOCIETY JOURNALmeans that a maximum of energy is retained within the instrument, a pre-condition to constitute a tone. The inherent tuning of a brasswind instrument can thus be ascertained by the location of these peaks, also called resonances. To a certain extent, the amplitude of the curves indicates the quality of response of the instrument. However, questions persist regarding the interpretation of these values. A commonly accepted rule of thumb is that a higher peak indicates a better response.
Figure 2 shows the input impedance curve of 13.301 and its related tones. A detailed overview of frequency ranges, measuring accuracies, and the usage of this method is given by van Walstijn et al.13 The measuring tool used in the present research is the Brass Instrument Analysis System (BIAS).14 The pitch of the original instrument is a1 = 448, which sounds as bf1 with the slide closed. Figure 2 displays the impedance of the instrument without crooks. The author chose to analyze 13.301 as an instrument in Bf with the slide completely closed, since analysis of it as sounding in A at a1 = 472 Hz would have involved considerable additional effort to adapt the measuring method. Using the original tuning bits preserved with the instrument, it is possible to tune it down to 440 Hz, thereby making it usable for performance with other instruments at a1 = 440.
In 1869 the instrument was relocated from the Accademia Filarmonica to the Museo Civico in Verona, but it was returned to the library of the former institution in 1969.15 At that point the instrument was in urgent need of preservation measures (see Figure 3a) and consequently underwent restoration in 1990 by Heinrich and Max Thein of Bremen.
Their restoration was conducted with extraordinary care and the outcome is a testament to their craftsmanship and attention to detail. The Thein brothers carefully marked the added parts, though further analysis was required in order to identify clearly the original parts. A useful clue for identifying tubes made after the mid-nineteenth century is the absence of a soldering seam. The technique for manufacturing seamless tubes was first developed in the nineteenth century because of the need for such tubes in steam engines.
These tubes had to withstand high pressure that would have caused soldered tubes to burst. William Aitken describes the attempts of both Charles Green in 1838 and Thomas Attwood in 1850 to develop manufacturing techniques for seamless tubes.16 It seems, however, that George Fredrick Muntz’s process, patented in 1852, was the first to achieve production.17 As early as 1864, six different factories in Birmingham produced 8,500 tons of seamless CuZn38 tubes, specifically for use in steam engines.18 The Wieland Werke, a brass manufacturer at that time in Germany, produced seamless brass tubes from 1865 on.19 The absence of a solder seam thus identifies a tube as being from the mid-nineteenth century or later. All of the tubes on 13.301, including the slides and crooks, have solder seams, which is an indication that they probably were made before the mid-nineteenth century. However, the older technique of tube-making could also have been used after the introduction of seamless tubing.
VEREECKE 29 Marks at 3 cm from the end of the bell indicate that the garland once rested loosely on the bell; Figure 3 shows that it was reattached to the bell when it was restored. Some minor dents have been removed. A piece of conical tubing has been added to the bell, as shown in a detail in Figure 8. The bell cross-brace and the first slide-brace have been reinforced.
Figure 3: (a) 13.301 before restoration (Verona, Museo Civico);
photo anonymous, © Accademia Filarmonica Verona.
(b) 13.301 after restoration (Accademia Filarmonica); photo by Maurizio Brenzoni.
The mouthpiece is engraved with the word “NVRMBERG” and is composed of three parts: the shaft, which is made from sheet brass; a soldered ferrule; and a turned cup. The mouthpiece has a cup diameter of 23.1 mm (see Figure 4). It weighs 42.8 gram and intrudes
26.7 mm into the instrument. A ferrule made of sheet brass covers the solder seam, thereby strengthening the assembly of the shaft. The wall thickness of the shaft is 0.35 mm; it is cylindrical at the soldered end but conical from the middle to the distal end.
Figure 4: Mouthpiece preserved with 13.301. Photo by Michele Magnabosco.
30 HISTORIC BRASS SOCIETY JOURNALApart from the flat rim, specific cup form, and bore diameter, the most striking feature of acoustical design of this mouthpiece is the form of its backbore (see Figure 5).
The larger diameter of the throat of the mouthpiece required a reverse-conical (actually, “belly”-shaped) backbore in the shaft so that it could fit into the smaller diameter of the mouthpiece receiver. This type of backbore is to be found in several surviving sixteenthcentury brasswind mouthpieces. Mouthpieces used for performance on early trombones typically have a flat rim and a bowl-shaped cup, but are turned from one piece of brass, implying a modern, conical back-bore design. The question remains: What is the acoustical significance of playing on a mouthpiece with belly-shaped backbore rather than one in modern style?
Figure 5: Bore profile of the Verona mouthpiece with characteristic belly-shaped backbore.
Acoustically, the highest pressure point inside the instrument is at the mouthpiece;
therefore, tiny changes to any part of the geometry of the mouthpiece will have appreciable effects on playing behavior and radiated sound. The mouthpiece has two main acoustical functions: it lowers the high resonances and it boosts the instrument’s resonances in the area of the mouthpiece’s own resonance. A historical mouthpiece usually has two such resonances (see Figure 6). Their positions along the frequency axis will therefore greatly influence the acoustical characteristics of the instrument. The three major acoustically important parts of the mouthpiece are the cup, the throat, and the backbore. Of these, the cup volume and the design of the backbore exert the greatest influence. The volume of the cup affects both tone quality and pitch and can alter the latter by as much as 35 cents.20 Enlarging the throat diameter has the same acoustical effect as decreasing the volume of the mouthpiece: it increases the resonance frequency.
The backbore is more important than the bore diameter of the throat and can alter the pitch by as much as 30 cents. In order to investigate the specific effect of the belly-shaped backbore of the Verona mouthpiece, an exact copy was made, together with another, using a modern backbore design, keeping all other dimensions the same. Both mouthpieces were made with the same tools and have the same cup and throat diameter; only the bore VEREECKE 31 design was different. The shaft of the original mouthpiece was measured from the outside, so that by subtracting the known wall thickness, the bore profile could be determined.