Arsalaan, Welcome to the Router Forums!
That is a beautiful musical instrument you have produced! Congratulations on the excellent work. I do a bit of work with Crepe Myrtle - large diameters and that is the hardest wood I have ever worked with. It makes other "hard woods" look like peanut butter by comparison. It is a difficult wood to work with, but absolutely beautiful when finished. I found that MicroPlane tools will cut through it better than anything else that I have tried. Some of the MicroPlane tools are hand-held and others are designed to be "chucked-in-a-drill". I most often use mine when mounted in my drill press. In cleaning-out my (late) Dad's workshop, I came across a very heavy duty flex shaft that will connect easily to the drill dress. When the MicroPlane is then chucked in the business end of the flex shaft - you may have what you're looking for.
But let me warn you: It's kind of like watching a cat fight! It can be very difficult to get a feel for it at first - so start on scrap wood first!
I hope this helps!
Otis Guillebeau from Auburn, Georgia
OPG3 Tweak everything!