What is the best word for someone who writes the books of musicals?

Forgive if this has been asked before - I wasn't sure what exactly to search. Please also forgive me if this is a really dumb question.

What is the best thing to call a person writes the books of musicals, but NOT the lyrics. I sometimes say "book-writer" but that sounds so clunky and weird, like saying "music-writer" instead of "composer." There's "librettist," but to me that implies they also wrote the lyrics (or am I wrong about that implication?). There's "playwright," which is accurate in a sense, but doesn't quite communicate the fact that they write MUSICALS. Many books of musicals are written by people who also write plays, so they can still call be called a playwright - but what about a writer who only writes the books of musicals and NOT plays?

What do you think? Is there another one I'm missing? Am I being too restrictive with the definitions I mentioned above?

Updated On: 5/9/16 at 05:23 PM

"what about a writer who only writes the books of musicals and NOT plays? "

That's so restrictive, though. It might be personal preference, but I don't see why or how a person who does this is different than a person who only writes plays (and hence is a playwright). Musicals are plays, so the storyteller (book-writer) would be by default a playwright.

madbrian said: "Librettist?"

I believe librettist is the right term. Quoting Wikipedia: " In the context of a modern English language musical theatre piece, the libretto is often referred to as the book of the work, though this usage typically excludes sung lyrics. " And a librettist is one who writes a libretto.

Not clunky, super fancy sounding in fact! But I think book-writer works also.

I also remember Hamiltome mentioning Lin became the librettist because he had to write all the bits to string together the numbers! Which wasn't the initial plan...

"Librettist" may be correct, but it is also ambiguous, since the writer of book and lyrics is also called the "librettist". Personally, I wouldn't call myself a librettist unless I had written both (which I usually do).

Calling the writer of the book the "playwright" is equally problematic because in the case of a musical, the "play" includes music and lyrics written often by others. What if we called the book writer the "author"? Same problem.

"Book writer" is no clunkier than "dressmaker" or "speechwriter" or "vice president". (It wouldn't be hyphenated, BTW, in any context that occurs to me. "Book" is the adjective; "Writer" is the noun. "Book-writing" might be capitalized if it modified a noun.)