I would agree with Colin that the trouble is most likely to be caused by a hard reed. A hard reed naturally wants to vibrate at a higher frequency and favours the high harmonics - which of course is also what you want to a certain extent to give a bright tone - but not too much. The problem is not scraping it so much that the squeaks go, but you also lose the brightness. However, a reed which is trying to produce high harmonics is either helped or hindered by various features in the chanter. What is happening when a note squeaks is that the chanter is being induced to produce a harmonic instead of the fundamental note - i.e. the vibrating air column is breaking up into sections. I may be open to correction in my acoustic theory here, and would welcome any input from people who have studied the subject in depth, but the basic situation is that an NSP chanter, being a "closed" tube, overblows at the 12th (2nd harmonic) which means the column breaks into three, and there are certain places on the tube - corresponding to these sections - where the harmonic can be very easily induced by leaking a finger or a key. Because of the overall length of the chanter, the place where any slight leak most easily starts the harmonic is usually around the low G, F# or E key. I have tried to correct squeaks by lengthening the chanter, as well as by inserting a longer plug in the end (effectively shortening it) and the result has often just been to move the "squeaking hole" further down or up - e.g. a chanter squeaking on G, with an extra length joined on the bottom, then starts squeaking on F# instead (My aim in using this technique has been to try and get the theoretical "optimum squeaking point" BETWEEN holes rather than just AT a hole, but it has not been very successful).
Another factor is that a small hole seems more capable of inducing a squeak than a large one, acting like the small "speaker key" on a clarinet, or like "pinching" or half-opening the thumb hole on a recorder. The first chanter I ever made, accurately copying an old Robert Reid chanter, and therefore very slender with thin walls and some really big "finger-sinker" holes, is almost impossible to induce a squeak on - even with a hard potentially squeaky reed. All the holes vent the full diameter of the tube and therefore sound the fundamental - just like successively cutting off bits of the chanter length instead of opening holes in the side. By contrast, thicker-walled chanters with small, neat holes squeak very readily when using the same reed. One can correct this tendency to a certain extent by undercutting the hole (downwards so as not to sharpen the pitch). However, once again it will not correct a hole which is determined to squeak and the only cure is to thin the reed and reduce its tendency to produce the harmonics. More random thoughts - another thing which induces the harmonic is a change in the air pressure - easing off the bag-pressure can do it, or suddenly increasing the pressure. Irish pipers overblow by putting down the chanter on their knee, suddenly stopping the air flow and starting it again - and of course NSP's do the same thing BETWEEN EVERY NOTE! Some other possibilities - 1) the key is loose in its slot so that it wobbles sideways and the pad doesn't always seat right on the hole. 2) the end of the key does not seat down absolutely square to the hole, and so one side "touches down" or lifts up slightly before the other. So to sum up - basically hard reed makes a chanter easily produce its natural harmonics, which form when the column of air breaks at certain points only - hence it's just the one key which makes the squeak. The harmonic comes when the chanter is PARTLY vented at or very near to one of those points. So, I've not got all the answers, but some of these ideas may help. Philip Gruar To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
