What is Regulation?
There are a lot of misconceptions surrounding the concept of 'Regulation'. Most players either have no idea what it is, or think that it is the answer to most flute mechanical problems. There are definitely the times when the key adjustments are put out and the adjustment screws are there to make everything right. But regulation can only fix this one type of problem. Other types of problems need to be fixed in other ways.
What is regulation? Have you ever noticed that most pads on the flute are linked to one or two other pads somewhere on the instrument? Regulation is the process of adjusting the keycups so that any set of linked pads will close together. If any of the pads remain open when the other(s) are closed - even if it is only slightly - the keys need to be adjusted so that all the pads close precisely at the same time.
Regulation cannot fix problems that are caused by bent keywork, warped or damaged tone-holes or a flute that is bent (even by a slight amount). It also cannot take care of pads that are worn, aging or leaking for any other reason. And regulation is almost impossible to carry out properly when the keywork is wearing away.
In fact, regulation is one of the final steps in any flute service or overhaul so it can only be done after all other servicing and fixing work has been completed. It is also one of the most important steps in flute repair. Your flute will not work without having this done.
If you take a look at your flute, you might notice that almost all the keys on the flute operate in conjunction with other keys. Very few keys move independently of the others. Only left-hand C, G#, Eb and the trill keys move completely independently. Low C# can operate independently, but there is still a connection with low C. All the other keys are connected with a series of pins and rods that line the inside of the hinges.
Regulation is the process of aligning each of the key groups, so that each of the pads in a group touch the tone-holes at exactly the same time. This will only work if each of the individual pads are sealing well on the tone-holes. If any of the pads do not seal well, the regulation step will fail.
How are the keys regulated?
There is more than one way to regulate a flute. The most common way is to wind the adjusting screws in or out, depending on the adjustment you wish to make. This is only if your flute has adjusting screws, usually found on student, intermediate and some lower end professional flutes.
If you own a high-end professional flute, it is more likely that you will not have any adjusting screws. In this case the keywork needs to be regulated using shims in between the key connections.
And that is all there is to it! Even though the concept of regulation seems fairly logical and straight-forward, there are different factors that can affect how it is carried out.
For one thing, the precision of the adjustment always depends on the judgement of the repairer... the pressure that is used on the keywork, the material that is used to feel the pressure, and the state of the pads themselves including the skin of that pad and the depth of the impression. Overall, the judgement will vary based on the method that the repairer uses to gauge the accuracy of the adjustment.
The work of manufacturers in their efforts to improve their flutes has led down the road to advice on the regulation of the keywork. Flutes that are adjusted appropriately (assuming it is made correctly) will play with an evenness of tone throughout.
There are times when regulation becomes sub-optimal when adjusted perfectly, and some of the top manufacturers are advising slight variations in regulation pressures for best playing results.