In music, the flat sign (♭) means “lower the pitch of the note by one semitone” (half step).

Here’s how it works:

• A semitone is the smallest standard step in Western music — like moving from one piano key to the very next one (black or white).

• For example:

  • B lowered by a flat becomes B♭.

  • E lowered by a flat becomes E♭.

Flats appear in two main ways:

1. Key signature – tells you certain notes are always flat throughout the piece unless changed by another sign.

2. Accidental – placed before a note, meaning “play this note one semitone lower than usual” for the rest of that measure.

An easy way to remember:
If a note is flat, it’s been “pressed down” one small step.