Tonal Finishing – Making The Theatre Pipe Organ Sound Great!

Ever hear the term "Tonal Finishing?"  We attempt to sort it all out here.

Just what is "Tonal Finishing"? It is a process that has been around for centuries and is practiced by organ builders worldwide.  Also known as "voicing" or "regulating", the process is meant to meld together the sounds of the various pipes and ranks in the instrument to create a series of gorgeous ensembles.

Tonal finishing takes place at the end stages of building or refurbishing an organ, and is clearly the most important step in achieving perfection.  An organ cannot be properly regulated at the factory. The effects of the size of the organ, the resonance of the chambers, the size of the venue, and the acoustics of the building all come into play.

Once the initial installation or refurbishment of an organ is complete, what you really have is sets (ranks) of tin, wood, and sometimes brass whistles operated by an air turbine, and controlled by a console.  An exact tuning of every pipe and rank in the instrument will enable the playing of music, but what will the music sound like?  Unless you are unusually lucky, Not Much!

In addition to regulating each rank, note by note, to ensure even volume within the rank, the volume or power must be adjusted so that the ranks blend and complement each other, and one does not drown the other out. Building a set of "terraced” ensemble volume levels in the organ that are each coherent, yet work together to build larger ensembles, is the ultimate goal in organ tonal finishing.  In addition, the speech or tonal color of many ranks can be adjusted, particularly the reeds, to vary the brightness of the tone from mellow to raspy.  Ranks can also be "contoured" so that the sound varies from the bass register up to the treble.

Voicing Reed Pipes:

Reeds have two major parts that determine the overall tone and volume. The first is the resonator, the familiar pipe tube that is sometimes cylindrical (clarinets, krumets), sometimes conical (tubas, trumpets), and sometimes capped (vox humanas, French horns).   The second, and hidden part, is the reed (also known as the “tongue”) and the shallot on which it is held. This assembly is at the bottom of the pipe (resonator) and is contained in the block where the resonator ends.  The mechanism of reed and shallot is mounted into the block and housed in the boot of the pipe, which can be removed to allow the technician to work on the reed.

The sound of a reed pipe is the result of a combination of factors including the shape and style of the resonator, its harmonic length, and the metal out of which it is made. (For example, Wurlitzer used brass for its trumpet resonators because they felt that it had a better, more orchestral sound.) Also contributing to the sound of the pipe is the reed and shallot. The reed is a thin piece of metal (brass or phosphor bronze) whose thickness is measured in thousandths of an inch.  (The reed takes its name from the bamboo reed used in the common clarinet or saxophone.) The shallot is the hollow brass tube with a flattened face and an opening in that face against which the reed vibrates. The physical configuration of the shallot affects the type of sound produced as does the shape of the reed.  A thinner reed tongue generally gives a brighter sound.  A thicker tongue, especially one with added weights (like a high pressure tuba), gives a darker sound.  The amount the reed moves away from, and back to the shallot in its vibration is the reed's amplitude and causes the pipe to be either louder or softer.  The greater the amplitude of the reed, the louder the pipe will be when it is in pitch.  Adding "curve" or decreasing "curve" at the bottom of the reed, changes its amplitude.  The voicer adjusts the reed with a specially shaped tool called a curving block (a heavy piece of metal with one or several different curve forms in it).  He/she puts the reed on the block, and applies "curve" (or decreases it) by rubbing the reed with a burnishing tool.