CELTIC-BREIZH for CITTERN or BOUZOUKI. (BREST is a port in BRITTANY). The tuning is as follows: DGCF. But it is simply a tone below the EADG typically used. The reason for this tuning is to gain a tonality approaching the MANDOCELLO.
I got the idea from John Santos first, to use chewing gum plus beeswax (again one of those recipes!). I had also learned that in India they mix the dough they use with FeO (black iron oxide) to give more gravity to the substance.