So "O Mistress Mine," which I've been playing for sheer love of its prettiness for a couple of decades now, out of the Fitzwilliam Virginal Book,--

turns out to be a much bigger deal than I'd thought. I had forgot: It's from Twelfth Night (one of the four or five Absolutely Magical Shakespeare plays); the lyrics (which, for their rank heterosexuality, I have always, wrongly, personally, disliked) are Shakespeare's own, and the tune (probably on commission from Shakespeare himself) is by none other than my own favourite tune-smith in all the world, Thos. Morley, not by Byrd as I had thought, who actually only just wrote the exquisite variations on it which are in the F.V.B.  Ah. Live and learn.