When In The Wee Small Hours was released, it came out on two 10” records. 10-inchers were the format for pop music & lighter music, but that’s not how Sinatra wanted it to be released. He wanted this record to be taken seriously. So, he wanted it to be released in the format that serious music at the time — Classical music — was released on: 12” records. Eventually, the album’s success convinced Capitol to release it as Frank wished: a Pop album on a 12” record.
We can quibble about who “invented” the 12” LP as a medium for serious pop music (Dinah Washington’s Dinah Jams was released in 1954, Live at Massey Hall by “The Quintet” was released in 1953), but there’s no doubt Sinatra was influential in the development of the concept album.
How Frank Sinatra Invented the Album | Polyphonic [YouTube]