Specific points of fact

There seem to be two issues of fact in question:

 Which instruments are correctly called ten-string guitars?
 How many resonances are missing from the six-string guitar?

Viktor maintains that the twelve-string guitar is also incorrectly named, which is the issue on which we first crossed swords. I did not at first understand why it was so important to him, but later I discovered that he believes and argues strongly that only Yepes-tuned instruments and some nineteenth-century harp guitars are correctly called ten-string guitars. Obviously, if a twelve-string guitar is validly called that, then for example a baroque guitar might be called a ten-string guitar, and his chance of having non-Yepes-tuned instruments excluded as he wishes is remote. 

So far as Wikipedia is concerned, the main question is this: What should be the scope of the article at ten-string guitar? It seems to me that, under WP:NC, it certainly includes instruments that are built and sold by Ramirez and Bernabe to identical specification to the ones that they built for Yepes, but fitted with a different 7th string (only) to accomodate a different tuning. In fact I would also include any other guitar called a ten-string by its maker, such as the B.C.Rich Bich 10. And if we include that, then where do we draw the line? Wherever that might be, it won't be where Viktor wants it I'm afraid.

So far as resonances go, Viktor has raised this in many other forums. In the ten-string guitar Yahoo! group he was recently asked to list the resonances of the six-string guitar, to clarify what he meant by a similar essay to the one above. He listed nineteen of them!

The point is simply, resonance in this context is not well enough defined to enable us to count them and arrive at a unique answer. Whether we describe the eight missing notes (pitch classes), supplied by four resonant strings, as four resonances or as eight is academic.

Marlow may well be wrong on many other things. We all make mistakes! But this particular issue is a non-issue. Viktor's real problem with Marlow is simply that she is popularising a set of tunings for the Yepes guitar which he does not like.