IN THE HEIGHTS and SUNDAY sounded pre-recorded, because of logistic reasons.
The orchestrations for GREASE, CRY-BABY, XANADU, and most likely CATERED AFFAIR were all expanded from the original sizes for the live Radio City Music Hall Orchestra.
GREASE: Trumpets and trombones were added to "Grease Is The Word".
CRY-BABY: I distinctly heard more strings, more trumpets, and more reeds in "A Little Upset".
XANADU: A wall-to-wall orchestral sound was added to the already-synthetic feel of "Don't Walk Away".
"How could she just suddenly, completely disappear into thin water?" - The Little Mermaid