Whatever you do, pal, don't use MDF as organ pipe material.  Whilst
being fine for some casework, the material is acoustically dead, with
no resonance.

If you take a proper wooden organ pipe and tap it lightly it will
almost ring, with it's own natural resonance, which enhances the sound.
MDF doesn't have this quality and will mean that whilst your pipe will
speak, there will be no warmth to the tone.

I know of an organ which has MDF soundboards and it has no warmth in
it's tone.  Stick to proper wood for organ pipes and soundboards, the
extra cost will be worth it.

Stephen Simpson