In the era before rock and roll number of copies sheet music a song sold determined its popularity?

In the era before rock and roll, the number of copies of sheet music sold for a song was a key indicator of its popularity. Sheet music was essential for most musicians who played at parties, events, and in public venues, and the more popular a song was, the more sheet music copies would be purchased and distributed. People would even pay to watch others perform popular songs and often the sale of sheet music helped promote a song's success.