I think one spirit in a scientist is to explain with a formula what
everybody else already knows. So, planning to finally make a few
reed pipe ranks, I spent some time trying to find out if there is any
theoretical basis for how big a reed pipe tongue should be.
Indeed, you can set up two different criteria, one for the tongue
resonance frequency, and one for the balance between tongue stiffness
and blowing pressure. Combining these criteria leads to unique solutions
for tongue length and thickness.
An interesting side benefit is guidance on how to modify the dimensions
should you make the tongue from different materials than conventional.
For instance, if you make it from bamboo rather than brass it will have
to be much longer and thicker because this is a very light material,
yet still quite stiff. Keeping a similar shape leads to louder sound.
[ See Johan's fine technical article about designing the tongue
[ for a reed pipe, including dimensioning diagrams for the novice,
[ at the MMD Tech site, http://mmd.foxtail.com/Tech/ -- Robbie