I'm not so sure about the latter part. Could you expound upon that? I'm vagualy familiar with a similar "infinite number of solutions" property with regard to t

I'm not so sure about the latter part. Could you expound upon that? I'm vagualy familiar with a similar "infinite number of solutions" property with regard to two cameras; however, assuming: * the keyboard is on a flat plane and, * all keys are on the same side of the plane that is defined by the line connecting the two microphones and tangent to the plane that the keyboard is on, shouldn't a well placed couple of microphones have a single solution (within the understood circle of uncertainty from sampling an analog signal) [edit: clarified my question] Actually, I think I know why it's not "that simple." All of my mental diagrams assumed you knew the time from key impact to the sound being heard by the first mic. This isn't the case. You only know the time between the first mic's experience of the sound, and the second mic's experience of the sound. Given that, you have a different set of constraints.