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Music 101: What Are Flat Notes? Learn About Flat Notes in Music With Examples

Written by MasterClass

Last updated: Nov 8, 2020 • 3 min read

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Western music contains 12 pitches, which are repeated over a series of octaves. Seven of these pitches are considered “natural.” These are the notes C, D, E, F, G, A, and B. The remaining five pitches are classified as either “sharp notes” or “flat notes.” Whether a note is sharp or flat depends on the key you are playing in.



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What Are Flat Notes in Music?

Flat notes are notes that sound a semitone lower than notes that appear on the lines and spaces of a musical staff.

  • As an example, the note B is represented on the third line of the treble clef staff. The note B-flat is indicated with that same notehead with a ♭ symbol placed to the left of it.
  • The ♭ symbol universally indicates a flat note. It tells a player to sound a pitch half a tone lower than the written note. For instance, the following image indicates the note A♭ on the treble clef.
A flat on treble clef

What Is A Double Flat?

You can also raise a note that’s already flat by using a double-flat symbol, which looks like this: ♭♭. In the following image, an A-flat is followed by an A double-flat.

A flat and A double flat on treble clef

What Is the Difference Between Sharp Notes and Flat Notes?

Sharps and flats fall into a musical category called “accidentals.” They represent alterations to “natural” notes like C or D or B.

  • On a piano keyboard, all of the black keys can be notated as “flats,” and can also be notated as “sharps.”
  • Any note can be a sharp or a flat—even white keys on the piano. For instance, the note B (a white key on the piano) can also be notated as C-flat. The note D (also a white key on the piano) can be notated as E double-flat.

There are two ways to think of sharps and flats: acoustically and in terms of music theory. As an example, let’s consider two notes: D#4 (the pitch D# in the fourth octave on a piano) and Eb4 (the pitch Eb in the fourth octave on a piano).

Acoustically, D#4 and Eb4 are the same notes. They both represent sound waves vibrating at a frequency of 311.13 Hz in standard instrument tuning. As such, if you were to play a D#4 and an Eb4 on the piano, you would be striking the same exact piano key. A person with absolute pitch would not be able to tell you one note is a D# while another is Eb.

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When Should You Use a Sharp vs. a Flat?

In terms of music theory, a note would be deemed either sharp or flat based on what key it appears in. This is because Western music is divided into groups of sharp keys and flat keys.

  • C major is neither a sharp key nor a flat key. It contains no accidentals—only natural notes. (The same is true for its relative minor key, A minor.)
  • From C major, we can follow the circle of 5ths and cycle through multiple “sharp keys”: G major, D major, A major, E major, B major, F# major, and C# major. Additionally, the relative minor keys of these key signatures are also “sharp keys”: E minor, B minor, F# minor, C# minor, G# minor, D# minor, and A# minor.
  • We can also cycle in the other direction from C major, and follow a circle of 4ths through multiple “flat keys”: F, Bb, Eb, Ab, Db, Gb, Cb. As was true for sharps, the relative minor keys of these flat keys are also considered “flat”: Dm, Gm, Cm, Fm, Bbm, Ebm, Abm.

As a general rule, “flat keys” get flat accidentals and “sharp keys” get sharp accidentals. Thus, to return to our notes D# and Eb, D# traditionally appears in sharp keys, such as E or B. Eb traditionally appears in flat keys, such as Ab or C minor.

So what’s more important: the acoustics or the music theory? Ultimately, it’s the acoustics, since that’s what listeners will experience. A listener doesn’t care if a piece of sheet music says D#4 or Eb4: she will hear the same exact audio frequency from her seat in the audience. And at the end of the day, that’s the most important thing about music: how it sounds to an audience.

Learn more about music theory in Itzhak Perlman’s MasterClass.


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