Uilleann Pipe Back D "Sinking"

This sound is the "back" D or 1st-octave thumb note dropping in pitch
even though pressure is increasing. In some cases the drop is sudden, as
in the accompanying sound file, and in other cases the drop is gradual,
such that the back D is really not stable at all.

Many acceptable reeds may do this if the back D is played with greater
pressure than desirable. However if the piper must take special care not
to overblow the back D in order to avoid the drop in pitch, the reed is
too sensitive.

Causes and cures are similar to back D "breaking" and can include: lips
too thin, heart (center area of blades) too thin, staple not appropriate
for chanter, staple eye too closed.

Sometimes excessively thinned blades can be revived by repositioning
the collar (bridle) to a higher location on the blades (closer to the
lips). This is reversible but has side-effects. The 2nd octave may
tend to become sharper; the lower 1st octave notes may become sharper
and the hard bottom D may become more difficult to obtain or may become
prone to gurgling; arbitrary individual 2nd octave notes may become
easier or harder to attain or hold; the reed may become sharper over-
all. Each of these side-effects can be treated after the collar is
reset.

The reed might be very sensitive to collar positioning, especially if
the collar was originally placed at the bottom of the scrape or lower,
down at the top of the staple binding. In such cases, very small (1/16"
or 1-2 mm) adjustments, followed by careful testing, are advisable.

Another simple but not-reversible treatment is to trim the blades
slightly shorter (1/32" to 1/16" or 1/2 to 1 mm). If the reed then 
is too strong, the blades may need to be sanded or scraped lightly
to restore the original strength and free vibration to the reed.

End of Uilleann pipe back D sinking text.