You don't need to look far in contemporary media to find examples of remixing. They can range all the way from someone taking a song and reimagining it, to someone chopping up a video and rearranging it to create something totally different, often hilarious. And although remixes are created off of the work of other people, I think the remixes themselves can have their own form of ownership.
A good example of this is the concept of music that uses samples from other songs. It happens a lot in EDM, but you'll often hear short soundbytes of other songs mixed in, and often times manipulated, to the song being played. I argue that it is the artistic style of the musician that drives them to incorporate a soundbyte in a certain fashion, to then also convey a different message to the audience listening to the song.
If someone writes a song using samples, is it their song? Or is it a collaborative ownership between every artist who's samples were used? Did those samples use samples? Especially in this age, so much of the music content has been reused and recycled from previous artists, that claiming that one piece of music is original is almost impossible. The big difference from then and now is the use of copyright laws to strike down users who infringe on those laws.
The use of these copyright laws, while mostly good, can badly affect both the artist and the listener, by limiting what they are able to write and use. If a particular riff sounds too similar to another riff, a lawsuit can form.
Even for non-musicians, particularly youtubers, it can be incredibly difficult to find music to use in monetized videos because so much music is blocked behind a copyright wall. If you use more than 30 seconds of a song, it's considered infringement, and your entire channel could be deleted, which, if that is your source of income, could be detrimental to your financial security. The fact is, a youtuber using a musician's song in a video will likely not affect the artist negatively, but the copyright law can absolutely destroy someone's career on the internet.
This all comes back to the question on who actually owns a remix? You could argue that an "original" song is actually a remixed version of another song, to some degree. You could argue that said song pulls influence from a previous artist.
In my opinion, it's no longer about who actually came up with the original idea, it's about who gets the copyright first.