- Do you agree that from experience and observation, we can tell that certain genres or fields appear to become completed?
- Does this concept or another concept best explain what is happening?
You're failing to engage the question of the nature of songs and music as a metaphysical level. I agree that mass culture and dissemination of works is part of the discussion, but it doesn't seem like you're trying to engage with that nature of "what is a song?". (See a number of the longer comment chains by other posters who provided thoughts on this topic if you're not sure what is under examination besides mass culture and dissemination.)
but it doesn't seem like you're trying to engage with that nature of "what is a song?"
The comment you're replying to did exactly that, actually. Since you seem to have missed that part, here's a hint: a song is a piece of music that's supposed to be sung by someone, i.e. it has lyrics, and a vocal part. Beethoven's Bagatelle No. 25 in A minor for solo piano (generally known as Für Elise) has neither: hence it's an instrumental piece, not a "song". (It's not even drawing overt inspiration from the song genre as a whole; but if it was,...