I've been working on a Theremin Excel simulation for the past couple of months. For those who don't know what a Theremin is, it was one of the very first electronic instruments to be invented, and has two "antennas" that independently change the pitch and amplitude of a tone via hand capacitance. The capacitive changes "seen" by the "antennas" during play are in the femto Farad range so it's quite remarkable that it works at all! The pitch antenna is vertical, ~500mm in height, ~10mm in diameter, and the player's hand moves horizontally nearer to and farther from the antenna on a line roughly perpendicular to the midpoint. I have an equation that gives me the free space capacitance of the pitch antenna and it seems to jibe with lab measurements I've made. But I don't have a good equation that will estimate the capacitance of a human hand near the antenna. For modeling purposes I'm thinking the antenna rod could be represented by a 2D rectangular metal plate, and the player's hand represented by a 2D square metal plate facing the antenna, moving along the playing centerline. Inputs to the equation would be antenna height, antenna width, hand height & width (the same since it's a square), and distance between the plates. Output would be capacitance. I've spend a couple of days pawing the web and trying to make sense of my old college texts, but can't find this problem or one like it solved. Could anyone please help me?