one day when I was practicing a noticed a slight buzz on my violas G string, open and fingered notes. I went ahead and checked the most usual suspects of buzzing ie the nut, bridge, strings, chinrest, tailpiece, fine tuners, shoulder rest, basically everything on the exterior of the instrument and could not find the source. I decided to let it sit for a night or two to see if it would go away. well, it did not. the next day I tried again and at first it sounded like the buzz had disappeared but soon after I finished warming up had it returned. this time, it buzzed not only on G but on C as well. I checked for open seams or cracks and could not find the problem. a few days later the buzz can sometimes jump to open D. I tried knocking my knuckles on the back of the viola and found that the knock sort of changes and I hear a slight vibration when I tap the back right side next to the right center bout. also when I knocked on the front next to the left corner of the fingerboard above the left f hole I got the same sound but nowhere else. after all that investigation I have no clue what this buzz is coming from. can anyone give me suggestions as to what it could be? I had been traveling the day before by plane, could that have caused something to unglue? sorry for the super long post but thank you!