All of the early sources, including Eisel in his teach yourself music book of 1738, say that the left side of the instrument bears the bass strings, made of brass, and the right side of the instrument bears the treble strings, made of iron. A number of the old instruments are reported to have preserved their old strings made of these materials.
The string materials can also be confirmed by comparing the speaking lengths of strings on either side; for example on Meiningen M4, the bass side c'' is reported to be 209mm, while the treble side c'' is 237mm. These lengths would confirm the use of respectively yellow brass and soft iron wire, at a pitch standard of approximately a=415 (Goltz 2012 p.319)
On the other hand, another instrument (V&A 910), measured by Chris Barlow, has the c'' strings at 246mm (bass) and 233mm (treble), confirming the use of soft iron on both sides of this instrument at a pitch standard also of about a=415 (Barlow, pers comm)
The old instruments all have slightly different ranges, but generally there is something like two-and-a-half to three octaves on the bass side and three or more octaves on the treble side, with a substantial overlap; it seems fairly normal for the lowest note on the treble side to be approximately one octave above the lowest note on the bass side.
The strings are arranged in courses, that is, grouped together with multiple strings for each note. The simplest arrangement would be to have only one string per note, but only a few of the old instruments are set up like this. Most have pairs of strings at least for the notes of the treble side, even if retaining single strings for the bass side. Many instruments have pairs for the bass. Some of the more sophisticated instruments also have triple-courses in the treble. It also seems fairly normal for the notes at the extreme of the range on both sides to have fewer strings, so for example a double-strung range will commonly end with three or four single-strung notes at each end.
These courses provide the notes of the diatonic scale. Additional single semitone strings provide a full chromatic scale but usually only for the central part of the range on each side. The semitone strings are always single, never coursed, and they are recessed behind the main rank by being run through slots cut into the nut and bridge.
Some of the more sophisticated instruments have extra bridges. For the lowest bass strings, a richer tone can be obtained if instead of a pair of strings tuned to the same note, the pair is tuned an octave apart. To enable this, a short bridge is provided halfway up the bass side soundboard, so that one of each pair has half the length of the other.
Many of the old spitzharfen have a feature on the treble side that is unusual and distinctive and gives a very particular tone to the strings. The strings are attached at three positions; the usual straight nut at the bottom, the usual curved bridge at the top, and a second curved bridge in the middle. This middle bridge almost exactly divides the strings in half, so that when one half (the lower half) is plucked, the upper half resonates freely as a sympathetic string, giving the instrument a strange jangling tone. The bridge pins on the middle bridge are notched to hold the string so it does not touch the wood, allowing the maximum jangling resonance. Usually on an instrument with this setpup, the lowest octave on the treble side runs full length to the middle bridge, with the double length section only for the shorter strings. The semitone strings are usually hitched to the middle bridge and do not have the extra resonating length.
Illustration: Museum für Musikinstrumente, Leipzig, 0388, from
Georg Kinsky, Katalog des Musikhistorisches Museums von Wilhelm Heyer in Köln, vol 2, 1912, p.25
The double sounding section of the strings on the right (treble) side is clearly visible, except for the lowest octave which have only the lower speaking section.
There are a number of instruments that have the two bridges, but the upper section of the strings is a lot less than half their length, as if the instrument maker saw the proper arrangement but did not understand its function or geometry.
An aparrently unique example is Boston 7.1773, which has on its treble side two different ranges. It is not clear to me how this would be tuned or used.
Simon Chadwick, St Andrews, Scotland.