Flat

Variation I:

Variation II:

Defintion: An accidental symbol placed to the left of a note, indicating that its pitch should be lowered by a semitone (half step).

The flat symbol alters the pitch of the note to which it is attached as well as any subsequent occurrence of the same note (identical line or space) in the same measure. Notes with the same pitch name, but a higher or lower octave, are not effected.

Source: OnMusic Dictionary