[kortex]

What is "diapason"? I looked it up and the closest definition was "a burst of sound", the rest pertained to pipe organs.

[nickserv]

I'd only seen the word used for musical instruments, where it refers to the scale length and/or the tonal range. Seems like here the same general idea when applied to an engine refers to its operational RPM (frequency) range.

[simne]

Band, range.