This instrument is made by Ganko in Japan.
He created Gank drum with his grandfather in 2007.
Gank drum is made by small propane tank.
But Gank 2 mini is selected material by Ganko.
Gank 2 mini of timbre is really clear and pure.
There are some variation of scale in it.
What Kentaro uses is "healing scale" include 528hz.
Kentaro usually use mallet when he plays it.
It makes miracle resonant especially in the small room.
If you are interested in Gank 2 mini, visit there ... Gank drum (Japanese)