Not a cage but an organ:
if he thought about it, he'd go insane.
Yes, if he thought about it
philosophically,
Instead of viewing himself as trapped in a cage (elevator), the operator compares himself to an organist to express the amount of control he has over the elevator’s activity – and, briefly, the lives of the passengers in his elevator. Actual organists have this same kind of control over their instruments. 
 
 There’s something insistent about the comparison, as though the operator is  willing  himself not to think of his elevator as a cage. As the poem progresses, we see that he’s been effectively trapped there by a society too prejudiced to allow him into occupations worthy of his talents.
Elevator Man 1949