Jack, the source of the music for these singers is a fascinating question.

The evidence strongly suggests that Hyslop's song was rarely if ever sung before 1866, seven years after its appearance under the new title "Scotland the Brave."

The title "Scotland the Brave" does not appear in Levy.

Surprisingly none of the 19th century UK/US newspaper runs I've been able to search seem to include any advertisement for any sheet music of "Scotland the Brave" (or "Scottish National Melody," for that matter). Literally millions of pages have been searched.

Here is an earlier example of a march with the right title played by a Highland regimental band:

Edinburgh Evening News (March 4, 1878):

"DEPARTURE OF THE 78TH REGIMENT FROM EDINBURGH CASTLE...On the Esplanade a small crowd soon collected, and as the men marched down Lawnmarket to the music of 'Scotland the brave,' the numbers rapidly increased."

A recent Wikipedia update eventually took me here:

https://archive.org/details/utahmusicalbouqu00unse/page/78/mode/2up

Flip to Number 79, "Praise to the Man." I'm not clever enough to read all the notes, but the first bars may well resemble today's "Scotland the Brave."

How about the rest of it? In a Mormon hymnal of 1878? The same year as the 78th left Edinburgh?? What the...????