and you deliberately took the lyrics and melody from another song, then changed the lyrics and the musical notes to your own but kept the same rhythm, do you reckon anyone would notice? Just talking about the melody here nothing else. Example:

"It's been a hard days night and I've been working like a dog."

you change it to something like

"The sun is beating down and everybody knows your name."

You've changed the melody and lyrics but the rhythm's the same and this is probably stupid cos they obviously wouldn't notice, seeya.