A person is singing acapella when outside noises cause him to change keys.

A soloist stood up to sing
so beautifully his voice would ring
unaccompanied and error free
his voice so crisp and right on the key.

The audience just sat to admire
‘til a truck passed going to a fire --
siren was in a different pitch
and it caused his untrained ear to switch.

Most hadn’t caught what it was about
then outside they heard a person shout
you guessed it – he changed key once again
which was noticed by most of the men.

It seemed smooth sailing until a clock
chimed and produced still another shock
by this time the people were aware
and each one of them started to stare.

Before he finished singing the song
he knew that he had sung much to long,
he had to drop his voice very low
when the old fog horn began to blow.