And Janis was imitating Bessie Smith, Big Mama Thornton and many others. Which gets back to my point of that everybody is basically imitating everyone else. Sometimes it’s unconscious, sometimes not, but it’s always there.
There really isn't anything new under the sun, is there?
Joni Mitchell accuses Bob Dylan of plagiarism. He chose the surname "Dylan" in honor of the Welsh poet Dylan Thomas. Mitchell undoubtedly was aware of Dylan Thomas and was familiar with his poetry. There is this lyric in Mitchell's "Chelsea Morning": "I will bring you incense owls by night." If I wanted to be snarky I would accuse her of borrowing from Dylan Thomas's "Fern Hill": "As I rode to sleep the owls were bearing the farm away."
Not plagiarism, but likely cross fertilization of half-remembered thoughts and phrases from many sources.