My favorites are the downbeat numbers (sometimes referred to as "music to commit suicide by"), especially "In the Wee Small Hours of the Morning."

Did you know that Frankie released two instrumental albums?

https://www.allmusic.com/album/frank-sinatra-conducts-tone-poems-of-color-mw0000212324

https://www.allmusic.com/album/frank-sinatra-conducts-music-from-pictures-and-plays-mw0000846907