How to tune the Chord Zither?

We had two chord zithers in our family, but eventually sold them because we had too many instruments.

One of the instruments had single strings, the other double strings like a mandolin. The names of the strings were painted on the bridge, so it was easy to tune them.

The basic design is to have the melody strings on the right and they are plucked with a ring on the right thumb.

The strings on the left hand side are organised into groups, each making up a complete chord;

e.g. one fat C bass string followed by thinner strings making up the chord: c e g.

Depending on the size of the instrument, there may be 3 chords or up to 6 or seven chords; melody strings can be diatonic or chromatic.