Uilleann pipe "hard" bottom D

This is a legitimate and useful sound effect which can be used to add
emphasis to the low D note on the chanter. It is triggered by a
deliberately-caused disturbance which creates extra or different
overtones, making the hard D brighter and louder than the normal
bottom D.

Usually the hard D is slightly sharper than the regular bottom D.
In the accompanying example it appears to be about the same pitch.

This can often be achieved with a combination of modifications. First,
a slight constriction such as an o-ring can be placed in the very bottom
of the chanter, and then the lower part of the chanter reed scrape
(often called the "V" can be slightly thinned and/or broadened.

These steps will tend to make normal bottom D less stable and thus more
tuneable while playing. As with many uilleann pipe paradoxes, the softened
bottom D will tend to become flatter instead of sharper as the pressure
is increased. These adjustments make normal bottom D too flat, unless the
piper deliberately under-blows the note.

The hard bottom D can be triggered by increasing the pressure to be a bit
higher than used for bottom D, while leading into the D with a short G or A
gracenote.

End of uilleann pipe hard bottom D text.