Regulation is the step after voicing; the further adjustment of the power and timbre of the pipes to suit the building. It is therefore carried out once the organ is installed, sometimes repeated over a longer period as the instrument settles in and develops, or otherwise to correct changes which have occurred over time due to dirt, dimensional changes to the pipework etc.
In reality, few theatre organs received detailed regulation once installed as timing and budget (not to mention availability of the organ) did not allow for this. In some cases, organs were almost thrown in and barely tuned prior to the theatre opening. In such cases, regulation can give startling tonal improvements.
Regulation involves detailed further adjustment to some of the parameters set by the voicer; such work has therefore to be carried out by someone with voicing skills, experience of and sympathy for the pipework in question. This work is often best carried out with a skilled helper in the auditorium who can guide the voicer in the overall effects of the adjustments being made.
Whilst a sympathetic classical organ voicer with experience of romantic instruments can usually carry out good regulating work on theatre organ pipework, one area often neglected is to regulate the stops both ‘off’ and ‘on’ tremulant, to achieve a consistent tremulant effect especially on reeds.