I'm not a lawyer, but my understanding is that while the "1640's violin composition" itself may be out of copyright, if I record myself playing it, my recording of that piece is my copyright. So if you took my file (somehow) and used it without my permission, and I could prove it, I could claim copyright infringement.
That's my understanding, and I've personally operated that way to avoid any issues since it errs on the side of safety. (Want to use old music, make sure the license of the recording explicitly says public domain or has license info)