Question

What invention increased the recognition of composers and made music more available?

Answer 1

This sounds like a test question, and without the context of the class you're taking we can't necessarily answer it well for you!

That said, I'd venture the guess that "sheet music" allowed composers to gain recognition.

Answer 2

Could also be the Radio, allowed the broadcast of music.

Answer 3

Broadcast is one thing, but recordings (particularly during the time in which radio was popular) tend to be credited to the recording artist, not the composer. With sheet music, composers themselves are credited directly.