John Nolte told the highly technical reason for extended boots for
Vox, Musette, and other fractional length resonator reed pipes.

To put all his very well explained technical words into your more
basic everyday organ guy talk: the reed boot is longer because the
reed doesn't care what resonator it resonates to.  It can resonate
to the boot or the resonator.

Making the boot extra long on a Vox forces the reed to vibrate to
the resonant frequency of the actual resonator and not the boot.
You will notice that without extension, the boot would be nearly the
same length, and therefore, near the same resonant frequency, as the
resonator.  Extending the boot puts it way out of the ball park for
the reed to use it as resonator.

Was this more clear?  Maybe, maybe not.

D. L. Bullock    Piano World    St. Louis

 [ Could the boot possibly be a Helmholtz resonator, like a jug?
 [ -- Robbie