OT: question on musical terminology

[NoSpam]

There seems to be a sufficient cross section of people here to answer most questions, so here goes with a musical question that is vaguely linked to DIY ... When writing about notes which are an octave apart, the higher note (I think) is marked with an apostrophe. An example is in the tuning descriptions of some older instruments, such as C18th English "Guittars", where the strings are tuned in two sets of three (CEG), with the sets an octave apart. This is written as CEG C'E'G'. The question is what is this terminology called and what is the convention for using it?

Dave

[Roger Mills]

Is this what you mean?

had to do a bit of delving into Wiki to find it!]

[Graham.]

I was just amusing myself and wondering if Heinrich Hertz and Helmholtz ever met, or collaborated, simply because of their like sounding names.

They did indeed, and in a totally different field of research.

always had a deep interest in meteorology probably derived from his contacts with Wilhelm von Bezold (who was Hertz's professor in a laboratory course at the Munich Polytechnic in the summer of 1878). Hertz, however, did not contribute much to the field himself except some early articles as an assistant to Helmholtz in Berlin, including research on the evaporation of liquids, a new kind of hygrometer, and a graphical means of determining the properties of moist air when subjected to adiabatic changes.[2]

[NoSpam]

What an absolute star! I have looked through music theory books, googled, asked several musicians and asked a music grad (my son!) but without success - less than hour after asking here I have the answer. Thanks!

Dave