Many people do not realize that the voicing on most metal pipes drifts out over time. The various parts of the pipe that produce the sound are composed of very soft, or relatively soft materials and the metal creeps as it sags (languids) or tries to return to round (upper and lower lips). This causes the articulation of the pipe to suffer and the pipe may start to try to speak the octave, simply become slow in speech, or begin oscillating up and down in pitch and sound like it is out of tune when it is the only pipe speaking. I once was called in to tune a fairly large 20 year old organ and was perturbed to find at least 12 pipes not speaking at all, having a hard time getting the fundamental, or oscillating up and down. Thin languids are particularly bad for this. We can rectify all these problems. We are also able to re-voice pipes and, in many cases, improve or change the tone and articulation to better suite the rest of the organ.
With regard to reed pipes, frequently tuners who are careless will change the voicing on the pipe in order to get it in tune quickly when they should find the reason why the pipe went way out of tune in the first place (usually a fly in the tongue or a weight that came loose, or a wedge that has come loose). Over time, with many of these ‘adjustments’ the rank begins to sound like each pipe is from a different set. The beauty of the original rank has been lost at this point and it just sounds like a cacophony. Or else someone with little knowledge has tried to revoice the rank to get a different tone, but has altered the tuning range, so in certain seasons the pipes cannot be tuned up to pitch, or down to pitch. Revoicing and regulating reeds is a specialty of ours. In some cases we replace the tongues with a thicker or thinner ones to give better tuning stability or tone. We can also alter weights and leather or un-leather shallots as the case demands.
The other consideration often not given organ pipes is that dirt accumulating in the windway or in the resonator or shallot can cause a decline in the proper voicing of the pipes. Reeds should be cleaned and wedges tightened and sometimes replaced at least every 15 years.
Most organists are amazed to hear the difference in their organ when the pipes are properly voiced for prompt articulation and evenly regulated. It can make a poor sounding and sluggish instrument truly come to life.