What's a bodhrán appliqué?
An applique in this example is something that is attached to a drum skin to affect the way in which it vibrates. Although it's still relatively uncommon, there are three main types of applique used.
A band of tape is affixed to the drum skin where it crosses the Bearing Edge. The purpose of the tape is to provide Edge Loading, a shock absorber, that can absorb many of the extra overtones leaving just the main ones and the fundamental. The idea comes from the Indian Tabla drum.
The weight or centre patch is again derived from the Indian tabla drum. Its purpose is to affect the main mode of vibration of the drum so that the skin moves in a particular way that generates a pure tone.
The double skin bodhrán is one offered by several makers. In this two skins are placed on the drum to provide a full bassy sound. I have not seen or played one but the opinions that I have heard and the anecdotes offered have been mixed in their support.