Not only do Arnaut’s remarks give a partial picture of the organ at this period, but contracts and other documents from other areas of Europe give corroborating details. Thus the organ at St Sebaldus, Nuremberg (by Heinrich Traxdorf, 1440–41), had Principal, Fourniture and Cymbale, perhaps of the type described by Arnaut. Such a division of the chorus became a kind of norm, not only at Nuremberg but also at the Florinskirche, Coblenz (1467), St Georges, Haguenau (1491), Weimar (1492), St Peter, Basle (1496), Leuven (1522) and in organs farther west. Yet it seems that the instrument of 1474–83 in S Petronio, Bologna, already had a large-scale, 50-note complement of nine single-rank stops (smaller in all respects than the organ as it now is), thus presenting a quite different tradition of organ building in the south.
Clearly the crucial questions are: how were stops separated, giving the organ different colours or effects, and why did builders of some areas give an organ several manuals while those in others concentrated on one manual? As to the second question, it can only be conjectured that southern builders learnt earlier than northern how to obtain musical variety from an organ with one keyboard, separate ranks and a long compass (e.g. the 53 or 54 notes at S Martino, Lucca, in 1473); and that northern builders, requiring only a few different effects (Diapasons alone, or the plenum), found that two or even three shorter or unequal keyboards with one or two registrations each were more useful and probably more powerful. Division of an organ into several chests was practical from the point of view of wind supply. As to the first question of how stops were separated, the situation is clearer. Several documents from the mid-15th century onwards refer to the varieties of sound achieved by a particular organ: Arnaut used ‘registra’; references in church archives include ‘registros’ (Treviso, 1436), ‘tirans’ (Aragon, 1420; Barcelona, 1480), ‘division de veus’ (Perpignan, 1516), ‘dreen gelueden’ (‘three sounds’, Grote Kerk, Zwolle, 1447) and even ‘a la moderna cum registri sei’ (‘with six stops in the modern manner’, Catarro, 1488). How were these varieties achieved? ‘Registers’ and ‘tirants’ (even five ‘registres sive tirans’ at Avignon in 1539) certainly suggest slider-chests (see fig.3b). After all, the Roman organ of Aquincum had latitudinal sliders, and its keys admitted wind to the pipes by these means. Longitudinal sliders running the whole length of a rank of pipes were different only in application, not in principle. However, when and where stop-sliders were first made is not known; no doubt they first appeared on small organs. A further system, the spring-chest (seefig.3c), was reintroduced in the Netherlands about 1520 to give greater reliability in larger organs, but was already known in Italy during the previous century: Orvieto Cathedral is said to have had an organ in 1480 with two spring-stops and two slider-stops. The most common 15th-century arrangement, particularly in the area from Rouen to Zwolle, was the ‘double chest’, useful especially for Chair organs. In such a chest the channels were divided into two parts, front (case pipes) and back (Mixture or Hintersatz), each with its wind box, the back one of which was provided with a shut-off valve allowing the Mixture to be taken off. Evidence for such chests is fairly clear from several Dutch contracts of the period (Zwolle, 1447; The Hague, 1487).
Much less clear is the origin of stopped pipes, although it is thought that the ‘double Principal’ of late 15th-century organs could imply an inner rank of stopped pipes sounding with the open case pipes, as well as multiple doubled ranks. ‘Coppel’ was a name used at first probably for case pipes (Limburg, 1471), later for stopped unison pipes (Bienne, Switzerland, 1517). Much the same may be said about the term ‘Flotwerck’ (Bassevelde, 1481). The ‘lead pipes’ for inner ranks referred to in contracts of many languages and areas have also often been assumed to be stopped pipes, but both documentary evidence and surviving Gothic pipework suggest that in many organs all interior pipework, including open pipes, was of lead. The Quintadena is a stopped metal rank sometimes referred to as Schallpfeifen early in the next century; it is possible that the emphasis on new organ colours at this later period was responsible for stopped pipes in general. Thus the stopped wooden Holpyp is authenticated from about 1500, but hardly before. Schlick (B1511) was still ambiguous about stopped pipes; even Flute stops at that period (e.g. Bordeaux, 1510) were open, as indeed they remained in Italian organs of a later century.
To sum up, in 1500 the average organ in northern Italy or southern France could be expected to have a chorus of ten or so separate stops, probably achieved with a spring-chest if the organ was somewhat large, with sliders if smaller; the upper ranks may have been duplicated here and there. Spain, at least in cities influenced by Flemish or ‘German’ builders (Barcelona, Valencia), followed more the transalpine organ. The bigger instruments of the Netherlands and Rhineland had two or even three manual departments, in most cases each with its own keyboard but all at the same (or octave) pitch. The English organ, judging by the All Hallows document of 1519–20 (see §8 below), was of the smaller Flemish kind: although it is possible that in secular or aristocratic circles Italian organs were known, all evidence points to the major influence in England being Flemish.
Some examples of organ schemes at their best before the turn of the century are shown inTables 1, 2 and3. That such schemes were distinctly regional can be seen in a 1000-pipe instrument built by the German Bernhard Dilmano at Milan in 1464–6, probably a large northern organ of Principal, Mixture, Zimbel etc. The instrument was updated in 1487 but still had only eight separate stop-levers in 1508. However, it is not known how many ranks of a native Italian organ of 1475 would be separate (as in later Italian organs). As to the sound of such organs, only conjectures can be made, even when much of the original material still exists, as it does at S Petronio, Bologna (conservatively restored in 1982). Although some contracts make it clear that specific sweetness or strength of tone was often required, much – perhaps too much – can be read into the use of words like ‘lieblich’ or ‘süss’ in early documentation.