In days past when Morse code was the common form of long distance
communication various codes were employed to speed up the transmission,
not too different to SMS of today.

These shortcut codes were known as "Q" codes that represented a
sentence; further, as a footnote, they are still being used verbally
today.  While I am not familiar with the music aspect of the enquiry
of this discussion, I am however guessing there is a crossover from
radio signal transmission into strip/roll music.

The explanation QRS in radio speak actually means "Shall I send more
slowly?"

Regards to all,
Doug Baker
Scarborough, Western Australia