There is nothing new in this phenemenon. It has been well documented, examples having been seen in a number of English speaking countries where folk clubs abound. (See "Strange Goings On in Folk Clubs" by Shirley & Curley). It is nothing more than the transformation of the male singer to the female singer, hence the rise in the scale. The wearing of shorts is the intermediate part of the process and in this hemispere one should expect the change to be complete by August. Then one should see twin sets, delicate linen tops edged in lace and voluminous flowing skirts, the voice having reached by then mezzo-soprano.