Currently working on Night Boat To Cairo. Everything super straight forward walking bass rhythm - but oh my the key!!
First few bars had a D♭ and a B♭ (or C# A#) The next part introduced an E♭ and an A♭ and now we have a G♭. Unless it's changed key and we have D#, F# and G# which is possible because we start outlining a chord of F where previously we have outlined F minor whenever it has cropped up.
Man this makes my head spin.
EDIT: and the tempo changes three times, and now it's started to slow down. So mu Italian is coming along "Ritardando" indeed.