This hit from the 70's is a classic. It appeared on Jackson's album Running on Empty in 1977 and it is in fact a version of an older song by Maurice Williams and the Zodiacs from 1953, although it was not released until 1960. See the original song here.

A LITTLE BIT= An emphatic form of "a little".

PROMOTER= The person or company that organizes an artistic performance.

DON'T= (coll.) The correct grammar should be "The promoter doesn't mind", but in very colloquial English we may find DON'T for the third person (he, she, it).

THE UNION= (AmE: labour union, BrE: trade union) An organization of workers for mutual aid and protection which helps and defends its members and negotiates their salaries and work conditions.

LEAVE IT ALL BEHIND= Forget about everything else (especially worries).

WON'T YOU...?= A polite way of asking a favour. We can use it in the affirmative or in the negative with the same meaning:
- Will you open the window? (= please, open the window)
- Won't you open the window? (= please, open the window)

SAY YOU WILL= Say that you will stay (will = want: say that you want to stay / will = future: say that you are going to stay)

ROADIES= Workers who load, unload, and set up equipment and often perform errands for musicians on tour.

The song was written by Williams in 1953 when he was 15 years old. He had been trying to convince his date not to go home at 10 o'clock as she was supposed to. He lost the argument, but as he was to relate years later, "Like a flood, the words just came to me."

Jackson Browne made this cover changing the lyrics a bit, so the song was addressed to the audience, begging them to stay for an encore* at a time when encores were an exception and not the rule as today.

*An encore is an extra song at the end of a concert. When the concert finishes and the singer says good-bye, people starts shouting "encore" (French for "again"), and the singer then sings an extra song.