This tutorial can be watched or read depending on your preference:
Step 1: Preparing for construction
You'll need an empty propane tank. Try and find a new one that has never been filled to avoid horrific injury. I found my at Wal-Mart in the camping section for $27.
A drill or dremel, a saber, jig, or similar electric saw, hack-saw blade, wrench, file, and electric tuner. If you do not have a tuner, you can use one of several tuner programs that install onto your computer and use a microphone. Try checking http://www.mymusictools.com/download/tuner-software/ for one of these programs.
Step 2: Removing the Valve
Step 3: Remove Welded Ring
Step 4: Preparing for the Cut
To prepare for the cut, drill small connecting holes or dremel out a slit long enough and wide enough to insert your saw blade. Proceed to cut along the guide you traced earlier stopping about 1/4" from the end. Do this for every tongue.
Step 5: Removing Magnetic Filings
Step 6: Tuning
Step 7: Playing the Instrument and Summary
I built mallets for my drum and I believe they provide a better tone. The mallets are simply two Spiderman superballs stuck on the ends of dowels. If you play with your hands, lightly tap the tongue about 2/3's of the way up to get the best tone.
My instrument was constructed for the state of Georgia's Science Olympiad where it won first place. It was used as the bass instrument and was therefore tuned much lower than what is optimal. I recommend you use the pentatonic scale Dennis Havlena uses for his.
All credit for this project goes to Dennis Hevlena, the inventor and original documenter. His site and instructions can be found at: http://www.ehhs.cmich.edu/~dhavlena/for-webpage-lp-hang.htm