He is then faced with the alternative of revising his play to suit
either: a) Jones, who can sing and dance, but is not funny; b) Smith,
who is funny, but cannot sing and dance; c) Brown, who is funny and
can sing and dance, but who cannot carry a love-interest and, through
working in revue, has developed a habit of wandering down to the
footlights and chatting with the audience. Whichever actor is given
the job, it means more rewriting.

Overcome this difficulty, and another arises. Certain scenes are
constructed so that A gets a laugh at the expense of B; but B is a
five-hundred-a-week comedian and A is a two-hundred-a-week juvenile,
and B refuses to "play straight" even for an instant for a social
inferior. The original line is such that it cannot be simply switched
from one to the other. The scene has to be entirely reconstructed and
further laugh lines thought of. Multiply this by a hundred, and you
will begin to understand why, when you see a librettist, he is
generally lying on his back on the sidewalk with a crowd standing
round, saying, "Give him air."

So, do not grudge the librettist his thousand a week or whatever it
is. Remember what he has suffered and consider his emotions on the
morning after the production when he sees lines which he invented at
the cost of permanently straining his brain, attributed by the critics
to the impromptu invention of the leading comedian. Of all the saddest
words of tongue or pen, the saddest--to a musical comedy author--are
these in the morning paper: "The bulk of the humor was sustained by
Walter Wiffle, who gagged his way merrily through the piece."