"john smith" wrote

Sine wave, square wave and things inbetween.
It's all about the "area under the curve".

There are methods to reduce the area above the sign wave within the
square wave, but they complicate the inverter design and can add volume
to the packaging.
snip
Pulsewidth modulation, an electronic means of making different length
square waves is an elegant solution, but adds cost and complexity.
snip

The Yamaha is supposed to have pulse width modulation, which if it is fast
enough, can come pretty close to sine wave, I guess.
--
Jim in NC