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.
Surprisingly clear information on video. First, learn to play a solo with only 4 notes. Of course, you can take it far beyond the lesson, using intonation, expression, style, different note-bending, polyrhythmic approaches, etc. Then...more notes! Great way to begin... And many more lessons available, even free, or for low-cost.