How are they tuned?
The four sympathetic strings are tuned in sets of 2. In the C/G tuning, two of them are tuned in unison to middle 'c' (same as trompette string), and the other 2 are tuned in unison to middle 'g' (5 notes above middle 'c', same as melody strings).
For tuning adjustments, zither pins are attached on the side of the instrument just below the headstock. A zither wrench is included as part of the package.