The Caribbean steel pan is likely the single most significant new acoustic musical instrument of the 20th Century. Some major developments incorporated by Felix Rohner of Panart have led to important instrument modifications. Among the differences to be discussed are as follows: using specified steel alloys in the sheet metal to replace commercial 55 Gal drums, sinking the pan in a press rather than by hand, surface hardening the playing surface in a nitride bath, dispensing with chiseled note section boundaries, adding a central dome to each note section, replacing the pan by a Hang (a lap-held instrument played by hand), and finally an additional air volume enclosed, to enhance low frequency resonances (the Gubal).