Guess case caps “Out”, but someone said it would come under
Short prepositions (three letters or less): as, at, by, for, in, of, on, to, but, cum, mid, off, per, qua, re, up, via – except when used as adverbs or as an inseparable part of a verb
Currently the RG is somewhat undecided https://beta.musicbrainz.org/release-group/47616c4c-5d4b-30f6-83bc-60e1c696b099
(also, Two Out of Three Ain’t Bad)
It’s not listed included in the list of short prepositions to lowercase at Style / Language / English - MusicBrainz, so I’d probably use “Out”.
https://www.onestopenglish.com/your-english/your-english-word-grammar-out/551420.article and https://www.macmillandictionary.com/dictionary/british/out_1 say that “out of” is a prepositional phrase, but that seems like it might exceed MB’s three-letter limit for short prepositions.
In the larger non-MB world, pretty much every web page I can find writes it as “Bat Out of Hell” (or “Bat Out Of Hell”). https://capitalizemytitle.com/ writes it as “Bat Out of Hell” for all of its supported styles.
Old conversation, but I was researching when “out” should be lower case and ran across this post at the CMS site about this exact situation that uses Bat out of Hell for its example.
Their conclusion is the same as mine: it might looks weird, but technically according to the rules, ‘out’ should be lower case in this title. “Out of hell” is clearly a prepositional phrase, and “out” and “of” are three letters or less. Out is not functioning as an adverb or part of a phrasal verb (because there’s no verb in the title), and can’t be considered part of any other grammatical or function that would exempt it. “Bat out of Hell” is an idiom; so the four words feel inseparable, almost like a name. But the grammatical function of the words don’t change just because they’ll be taken idiomatically; their function is still based on what they literal mean: Critter (noun) from (preposition) the Underworld (prepositional object).
I think “out” annoys of people for several reasons. One is that it still looks respectably big and weighty when capitalized. I bet most people would get the capitalization of short words exactly wrong with a title like “What If It Is Out There?” Most times capitalizing “out” looks OK even if it’s grammatically incorrect, but I agree with the posters on this thread about Miracles out of Nowhere looking annoyingly wrong if “out” is capitalized.
There are a ton of multi-word prepositions,, but because our threshold is three letters, “out of” is definitely the most frequent two-word preposition people here will see. “Out” is probably the word most evenly split between being used as a preposition or a non-preposition, so it always needs to be analyzed grammatically, and it’s one of the tougher words for people to figure out its function, especially when it appears as part of “out of”.
In some cases, it’s not even possible to determine from the title alone. I found this example:Running Out of Hope – “Out” is capitalized because “running out” is a verb phrase, and “of hope” is a prepositional phrase. But then I found Running out of Hope, Arkansas. I didn’t know this artist, so I looked up the lyrics online, and the title is meant literally: she’s singing about how she’s going to leave and never come back, so “out of Hope, Arkansas” is a prepositional phrase, and “out” should be lowercase. But there easily could have been a couple verses where she’s singing to her hometown about how she’s losing her faith,using wordplay to make the title mean both (Running) (out of Hope, Arkansas) and (Running Out) (of Hope), (Arkansas). We have no guidelines for that, so we’re kind of stuck unless someone can invent Schroedinger’s caps.
Edit: Incidentally, capitalizemytitle.com is broken for the word Out, capitalizing it even when the selected style guideline says not to. https://titlecaseconverter.com/ seems like it’s working correctly, even with phrasal verbs – try it with the titles look out the window and look out for number one.