It is also difficult to find gut strings by today’s standards; I did research on violin strings both gut and synthetic core. Gut strings are a natural fiber and are effected by heat and humidity and have a relatively short string life, meaning that the best sound quality only lasts a few years at best. Synthetic strings last longer and are not effected by temperature changes or moisture. Because the best sound can be heard on steel or synthetic strings for a longer time, these types of strings are typically found on student violins and new instruments. Rest assured that your tabby and calico cats are safe from today’s string market. I love cats and would only play on synthetic strings because I like the warm sound that wrapped polymer strings produce.