As a record-collector in the field, I can tell you that John McCormack had a tremendous audience among record-buyers in the American south from his earlier recordings c. after WWI until before 78 rpms ended their domination of the market c. 1950.

So much so, that I, hunting for genuine old time music and blues records in house after house from the Mason-Dixon Line south to the Gulf of Mexico, Atlantic coast to the Mississippi—the homeland of old time music and blues in their heyday 1920-1942—commonly found the traditional records outnumbered by shoals of McCormack's high-toned classical-styled pop-standard songs, 'Mother Machree' among the most numerous.

That Southerners continued this elevation of taste is confirmed by the equally tremendous popularity in the region of Vernon Dalhart, whose elegant vocals dressed up southern-themed folk and pop music during those decades. McCormack had clearly made a market for Dalhart.

Apparently—I imply no value judgments—the ordinary southern singing wasn't such a draw; traditional and early country music recordings never sold anywhere near so well.

After 1942, with the help of radio, musical styles broke with tradition and changed to recognizable modern pop, suddenly mutating into distinctly different R&B and country music. Which of course ended the saleability of McCormack and Dalhart too.

Admittedly I'm only stating the obvious. Funny how normal-seeming we assume that outcome is, though, considering all the deeper questions it raises.

Bob