Each word below can be preceded by the same letter, have its spelling changed, and, with the exception of the sound of the added letter, retain its original sound. What is the added letter, and what are the new words?

PIE
KEY
FEAR
EARLY
TOUGH

HINT:
The added letter is S.

Answers:

PIE - SPY
KEY - SKI
FEAR - SPHERE
EARLY - SURLY
TOUGH - STUFF 

Credit: LA Times Crossword
August 7, 2011
Donna S. Levin
S-WORD PLAY