mezzanine floor
like tepid tea

The real lyrics:
I'm at this bolted door, but I'm coming through without permission/If I go they say I'm wrong, if I stay there'll be no song

But I misheard them as:
I'm at this vaulted door, but I'm coming through without permission/If I go and say no more, will I still be your son?

The embarrassing moment of revelation:
Reading the liner notes

Age when I realized how wrong I had been:
18

Misheard by:
Adam

I am on special medication: yes