It's a little-known fact that before the 20th century there was no artistic production of any kind. ;)
In more seriousness, I'd guess that the traditional dominant sources of income for musicians were (a) patronage and (b) being independently wealthy; I doubt giving performances mattered all that much.
That's a very good point. I had an image in my head of traveling musicians playing lutes but that's a bit unrepresentative! Especially of music that has endured through time (e.g. classical composition).
Instead of patronage / wealth, I suppose that a market mechanism could be used to support music creation in a wider section of society. However, I would actually argue for income redistribution to support that.
In more seriousness, I'd guess that the traditional dominant sources of income for musicians were (a) patronage and (b) being independently wealthy; I doubt giving performances mattered all that much.