Sharps and Flats

A sharp , placed immediately before a note, raises the pitch of that note by one half step.

A flat , placed immediately before a note, lowers the pitch of that note by one half step.

The black note between A and B, therefore, can be referred to either as A-sharp or B-flat.

Likewise, the black note between C and D can be referred to either as C-sharp, or D-flat.

Click on the piano keys below to hear what the notes sound like.

Incidentally, accidentals don't just refer to the black notes. Any note can take a sharp or a flat, which leads to the famous

Musician’s Theory of Relativity