Quality manufacturer technical manuals are rare. For one reason, they are difficult and time consuming to create. For another reason, certain techniques are common to all pianos and many manufacturers just simply assume technicians know all the steps. However that can be a dangerous assumption.

Here are a couple technical manuals from Steinway and Kawai. They are all quite high quality and give you an idea of the detail involved in maintaining pianos at a high level.

Steinway Voicing

Kawai Grand Regulation

Kawai Vertical Regulation