Voicing is used to describe the loudness, softness, or the harmonic or tone quality of a pipe. It's the process by which tone quality of the pipe is regulated (as opposed to tuning, which regulates the pitch). Techniques include adjusting the shape of the tone-producing mouth of a flue pipe, cutting small nicks into the mouth, regulating the shape of the reed in a reed pipe, adjusting the size of the toe hole where air enters the pipe, and others.
For a visual explanation of voicing and quick tour of the pipe organ voicing shop,
The voicing shop is a large climate controlled room with entrances to both the workshop and the assembly shop. Two walls are lined with a double tier of pipe bins. In the centre of the room stands the 56-note, five-slider, two-pressure, mechanical action, voicing machine, with electric blower delivering up to 12” wg. Pressure and two bass blocks (single and 12 note). A large workbench lines the 3 rd wall, whilst a video monitor, telephone, shelves for brass, sheet metal, tuning-slide machine and stocks, and mandrels line the 4 th wall. A large work table stands next to the end of the voicing machine. John Gray (HN&B London) has been the Company's flue and reed voicer for its 39 year life and is currently teaching his wonderful skills to Christopher Templeton.