I read this article on a new music learning service/site called Chromatik. It tell of the advent of sheet music and how music in the days when Tin Pan Alley thrived was all about the song and not so much about the performance. I think you'll find it interesting.

The advent of sheet music as a viable business didn’t really take on until 1880 with the rise of Tin Pan Alley. Originally Tin Pan Alley only referred to a specific building on W. 28^th and 5^th Ave. in New York City, but eventually it came to represent an entire period of popular music dominated by music publishers and songwriters.

Since the early Renaissance-era manuscripts of monophonic chants, sheet music has been around in one form or another. As the printing press made waves in the 15^th century people sought to print music, but it was not easy at first. The first recorded printed book to include music, the “Mainz psalter,” (~1457) had to have the musical notation hand-written in. Yet as technology advanced throughout the centuries and songwriters eventually came together into a de facto publishing house, Tin Pan Alley came to represent an industry that was growing exponentially. Within the first ten years of the 20^th century songwriters and publishers were churning out upwards of 25,000 popular songs per year, the highest production of popular music ever.

Composers like Scott Joplin, Irving Berlin, George & Ira Gershwin, Andy Razaf, and others were creating what would be the centerpiece of popular American music for the next 50 years. It wasn’t until the rise of rock & roll that the face of pop music really changed. Yet, it was not only the actual music that was being charted; precedents were being set for the entire music business as an industry.

As more families bought pianos for their households, songs became the selling point. It wasn’t the performance or the artist, but the songs which thrived. Song pluggers were hired to go around performing the sheet music as a means to sell more of it. As a result it was this era that separated the performance from the song, thus creating the complex state of the industry we see today with songwriting splits and the likes for better or worse.

Courtesy of Chromatik.com