Please tell me what's the difference between "stand up tall" and "stand up straight"? There's a Sesame Street song named "I Stand Up Straight and Tall", which means there's some difference in position, right?
"Straight and tall" is a collocation. It strikes me as very old. "Tall" used to mean something like "good-looking", applied to people, and I think some of that connotation clings to this expression. The AHD shows an archaic definition for tall: "Excellent; fine." Webster's 1828 gives the "unusual" definition for tall "Sturdy; lusty; bold", which is nowadays impossible.

We don't normally say "stand up tall", it's "stand up straight". We can, however, "stand tall", meaning "have pride".
Students: Are you brave enough to let our tutors analyse your pronunciation?
Thank you, enoon, for your kindness!

Depends upon which "B" movie script and if it is a western, a musical or other type of movie or live performance.