As title, I’ve heard guitars for example are designed to be kept under constant tension and leaving one unstrung can cause the neck to deform - is this the case for shamisen, does it not matter, or should it be unstrung/loosened when not playing?
Hello there.
Best practice suggests to loosen the tension a little after playing in order to inhibit damage to the skin, lengthen the lifespan of the strings themselves, and help manage wear on the sawari.
Shamisen necks are often stored unstrung for long periods - it’s not something I’d worry about