A mandrel should be an essential part of every piper’s toolbox. The use of this simple appliance can make a huge difference to volume, pitch and vibrancy. The benefit of a mandrel cannot be overstated for pipe bands and soloist alike.
When adjusting a chanter reed there is a fine balance between mouth size and blade thickness. Concentrating on one while ignoring the other can be very detrimental. Some pipers will simply squeeze a reed to reduce the mouth size. This may indeed make it easier to blow because it will close the blades but it will also reduce the vibrancy and raise the pitch. The solo player may get away with this one sided solution but in a band situation, striving to get all chanters to the same pitch, it would be a disaster. Squeezing the blades together will raise the pitch, make the reed sound thin, decrease the vibrancy and reduce the volume.
When the reed mouth has closed too far the chanter will pitch high and will tend to have an unbalanced scale. This could also lead to a very sharp high G. Using too much tape to flatten the high G will give the chanter a tendency to 'chirp'. It is time to whip out the trusty mandrel and with a little twist open the closed end of the staple. This will open the reed mouth bringing the pitch down, balancing the scale and flattening a wayward high G considerably. Be mindful that opening the reed mouth will strengthen the reed and may make it uncomfortable to blow. A gentle scraping or sanding of the blades will ease the reed and increase its vibrancy and volume. (For instruction on scraping/sanding a reed see the Chris Apps instructional video.)
Finding the correct balance between mouth size and blade thickness with relation to pitch, strength, vibrancy and volume will take practice but the rewards will be worth the effort.