A reduction of the prominence of the thyroid notch should not have a long term effect on your singing voice if done properly, as only the anterior (or "front) surface of the cartilage is typically reduced, as your vocal folds (or vocal cords) attach on the posterior (or "back") surface of this. This should not have a long term effect on your singing voice. However, as it has only been one month since surgery, there is a chance that local swelling can account for the change in pitch, as your voice is the most finely tuned instrument there is, and it takes just the smallest disturbance to throw this off of tune. That said, I think that at the one month point I would wait, as local swelling in the surrounding area after surgery is expected. Laryngoscopy and stroboscopy would tell you much more, though my inclination is to give it time. These would be especially helpful if you had preoperative exams to compare to, which singers often do. Summit Kundaria, MD Nuance Facial Plastics Charlotte, NC