Although I haven't mentioned fiction yet in this discussion of tone and audience, fiction titles definitely have a tone as well. Consider P.S. I Love You – Can you possibly have any doubt that this whispery, girlish title is intended for an audience of young women? And how about this: Support and Defend? It sure isn't "chick lit." Combined together, "support" and "defend" are two very manly and militaristic words.
Let's consider Neuromancer, which isn't a word in the dictionary. Anybody with a feel for language, though, will perceive that it has a geeky tone, and therefore the novel concerns something technological and futuristic. It's also probably bleak rather than upbeat and happy.
By the way, with nonfiction, you may want to name your audience explicitly. Money-Smart Secrets for the Self-Employed, for example, clearly indicates who the content applies to. The same goes for A Single Man's Guide to Easy Meals, which implies in just seven words that if you're an unmarried man, the book is for you even if you don't know how to boil an egg.
Make sure that your word choices and tone are not only right for your audience but also consistent with your branding. I had an opportunity once to write one of the books in the "Dummies" series, and I turned it down because I'm known to be a smart person who enjoys bright, ambitious clients. How do you want people to perceive you? Your book title needs to match your overall image and not be nastier, edgier, sweeter, or more religious than you normally are.
Earlier in this course, I mentioned the book Zilch: The Power of Zero in Business. Imagine if the author, Nancy Lublin, fell in love with the Yiddish word "bupkis," which, like "zilch," means nothing, and decided to call her book Bupkis: The Keys to Radical Bootstrapping. The meaning is roughly similar to her actual title, and it also has some nice alliteration, but the tone is completely different. Lublin would need to decide whether her audience would be familiar with and/or accepting of a Yiddish title, and whether that fits with her branding. My experience is that most Americans outside of big cities on the east and west coasts are not familiar with Yiddish words that people in Hollywood and New York City tend to know, like "gonif" (thief) or "maven" (expert), and the author of this book might or might not want to tie herself to the Jewish community. I'm totally speculating here, of course, since I do not know Nancy Lublin.
If you can't be objective about your various title alternatives, do a kind of eyewitness lineup. Give someone who doesn't know you or your book project three to five different book titles and ask them to tell you what they guess about the book, the author, and the audience for each of them. You may be shocked at what you hear! But better to be shocked now than in your reader reviews or poorer-than-expected sales.
In the next lesson, we consider sound and rhythm as elements of titles.