laws governing musical plays that at certain intervals during the
evening the audience demand to see the chorus. They may not be aware
that they so demand, but it is nevertheless a fact that, unless the
chorus come on at these fixed intervals, the audience's interest sags.
The raciest farce-scenes cannot hold them, nor the most tender love
passages. They want the gurls, the whole gurls, and nothing but the
gurls.

Thus it comes about that the author, having at last finished his first
act, is roused from his dream of content by a horrid fear. He turns to
the script, and discovers that his panic was well grounded. He has
carelessly allowed fully twenty pages to pass without once bringing on
the chorus.

This is where he begins to clutch his forehead and to grow gray at the
temples. He cannot possibly shift musical number four, which is a
chorus number, into the spot now occupied by musical number three,
which is a duet, because three is a "situation" number, rooted to its
place by the exigencies of the story. The only thing to do is to pull
the act to pieces and start afresh. And when you consider that this
sort of thing happens not once but a dozen times between the start of
a musical comedy book and its completion, can you wonder that this
branch of writing is included among the dangerous trades and that
librettists always end by picking at the coverlet?

Then there is the question of cast. The author builds his hero in such
a manner that he requires an actor who can sing, dance, be funny, and
carry a love interest. When the time comes to cast the piece, he finds
that the only possible man in sight wants fifteen hundred a week and,
anyway, is signed up for the next five years with the rival syndicate.