Here's the most intricate process of piano technology - the regulation of the action. Note the weights used to "measure" how much pressure is used to depress the key, the adjustments made to reduce or increase resistance of the key, the flame used to bend the hammer shank so the hammer hits the strings properly. This is a very good "overview" of a job that can take up to two to six days to complete!
Notes From the Piano Bench
Questions and Answers and updated factoids concerning pianos in the 21st Century.