Obviously, something's radically changing today in the way we pay for music, who winds up getting the money, and which performers get rewarded.
But, beyond all the talk about Spotify and copyright and "I didn't learn guitar to sell T-shirts," how unique a case is the contemporary music industry?
Is the idea of having a very few "star" performers and a lot of talented & dedicated amateurs (most with day jobs) really a new way of being, or does it resemble the way things were before LPs? Or printed sheet music? Or some other factor?
Historians, where do rock stars come from?
Are "rock stars" historically unique?
I think they are in some ways, but not in others.
Were there extravagant musicians who became very wealthy and toured a lot of countries? Yes, there certainly were some of them. We know of super famous singers in the past, /u/caffarelli will be able to tell you about singers, and will probably enjoy telling you about a specific subset of those (you might not expect what she is going to write about).
The names of Niccolò Paganini (1782 – 1840) and Franz Liszt (1811 – 1886) usually come up when talking about this. The first was a violinist, and some kind of cult was developed around him. The same happened with Liszt (he was certainly inspired by Paganini's success), and we have Lisztomania. People got really crazy: fans were fighting (as in physically) to get handkerchiefs or gloves used by Liszt; they would try to forcefully get locks of his hair; they collected his coffee dregs and cigarette butts.
Is the idea of having a very few "star" performers and a lot of talented & dedicated amateurs (most with day jobs) really a new way of being
Well, there were few top performers. And then you had professional musicians of lesser status. Were there amateurs? Of course. But those amateurs didn't really want to become rockstars. They were not exactly a role model. Many royal/noble/wealthy people were competent musicians (and some were extremely good), but it would be completely insane for them to want to become "a star" since it was not a proper thing to be.
As far as I know, it was not common for people to dream about becoming the next Liszt. The musical profession was not prestigious.
The reactions to the deaths of Beethoven (1770 – 1827) and Chopin (1810 – 1849) are also what you would expect for an early rockstar. Beethoven's funeral procession was big, thousands of people (10k-20k?).
Chopin's funeral was delayed for a couple weeks after his death, and only ticket holders were allowed into the church (people arrived from many cities, thousands had to stay outside). The entire façade of the church was draped in black velvet. If that is not a rockstar's funeral, I don't know what is.