I have a PhD in English literature and have taught several university-level courses. If a student reads 10 open source papers and uses their ideas, that is plagiarism. Paraphrasing the intellectual property of others is plagiarism. Rewriting quote by quote is one very serious kind of plagiarism, but it is by no means the only kind. Knowledge-gathering involves citation, building off the work of others. You can definitely plagiarize by using ideas from ten articles -- they're not your ideas, plain and simple. Just because you're stealing from multiple sources doesn't make it not stealing.

If I break into ten homes, and steal one copper pipe from each house, then melt that copper down to build one really big pipe, have I not stolen the copper? Am I not a thief? Just because the material is sourced from many places, doesn't make it not plagiarism.

Some music does contain plagiarism, but what you're talking about is what usually falls under the umbrella of "fair use" (transformative works, parody, inspiration) or "sampling," which acknowledges the original creator.

General knowledge does not fall under the realm of plagiarism. Inspiration does not equal plagiarism, so long as the new idea is yours. You're comparing apples to oranges to justify a program that steals from artists.