Didn't read the full article, but couldn't you argue that with audio recording and distribution 1 hour of string quartet playing labor can yield many more person-hours of string quartet listening in 1965 than 1865?
Studio recording is a different type of labor, to produce a one hour record musicians should put at least 6-8 working hours. This is for quartet, bigger orchestras will tend to take even longer to properly record. We also need to factor in a work of recording and acoustic engineers, equipment and sound stage cost.
But to be precise, one full take of one hour recording will still take exactly the same amount of labor from musicians)
The whole idea of record distribution is actually a different type of economy. Live broadcast would be an interesting twist in this path of reason, but it was not a thing in 1960s.
