This is a follow-on to How can I determine what elements of a work are covered by a copyright mark? which dealt with sheet music for public domain compositions that, nevertheless, claimed copyright protection. The current answer points out that editorial decisions and modifications to a public domain work are certainly subject to copyright, but intriguingly suggests, "Even the layout and typography or engraving are subject to copyright...."
If all "layout and typography" are subject to copyright then any writing or printing of otherwise public domain content is protected. But it seems unlikely that the "threshold of originality" can be surmounted so trivially. (Answers to related question Copyright status of restored works indicate that mere "restoration" is only afforded protection in countries that follow a "Sweat of the brow" rule.)
So, disregarding essential creative content like words or notes that we normally consider as subject to copyright (and which can pass into the public domain long before interest in a classical work fades): What visual elements of a printed work are eligible for copyright protection?
Consideration of the following examples might illuminate the question, but need not be explicitly addressed in an answer.
If I hand-write a verse of Shakespeare, can I claim copyright on my manuscript because my handwriting is original?
If I type a chapter of the King James Bible can I claim copyright on my pages because of where I decided to put carriage returns or tab stops?
Can I claim copyright in my transcript of John Locke because of my "original" selection of font, pitch, and typographical layout?
If, as suggested above, I transcribe a composer's original score, is my transcription protected without satisfying any other creative criteria? If not, what criteria suffice?
If I make it more legible and alter the layout simply because I use computerized notation software? (This would seem to be analogous to using a word processor to transcribe words written or printed more than a century ago.)
If in some place I use a different but musically equivalent notation? (This could be considered analogous to using a more modern spelling, or writing "e.g." instead of "exempli gratia.")
If I make changes that are literally different but practically insignificant – e.g., where the composer wrote "Lento" I write "Adagio?" (One might equate this to substituting synonyms for some words in an essay.)
If I make changes that qualify as corrections? (In the writing analog, I correct typographical or grammatical errors.)
If I add or modify notation that is musically significant – e.g., slurs or ornaments?
If I annotate musical dynamics – which may have been implied and even widely understood among modern performers – not found explicitly in the original score? (E.g., forte, crescendo, ritardando, staccato.)
If I annotate fingerings or bowing instructions, which when significant are generally obvious to an experienced musician but which can be helpful to a less skilled player?
