>On a similar theme perhaps were aught to limit the number of guitars?

Absolutely! And I speak as a guitar player. I will often not play if there are other guitarists there unless there are a decent number of 'melody' instruments. It seems silly where you may have, say, a whistle and a mouth -organ and three guitarists trying to accompany.

Then there are the guitarists who play the wrong chords or in the wrong rhythm and, despite that, thrash the guitar so that people in the next street are wincing.

Having said that, guitars are useful in that they were designed the way they are precisely for blocking out concertina players. After all what have concertinas, (the only instrument designed by an Englishman), got to do with Irish or Scottish music? : )