What do the following phrases have in common?

SHARP TONGUE
ATOMIC NUMBER
TEN POUND SACK

Answer:

Each phrase contains a word that can be represented by the symbol #:

# TONGUE
ATOMIC #
TEN # SACK

NOTE: On close examination the musical symbol for sharp is different than the symbol #. This is to prevent it from being obscured by the lines on the musical staff. But the # symbol is commonly used for the musical sharp.