If we can get away with just having sharps (aka black notes on a piano) then why complicate things and add flats as well? For example, if I have a C# why call it Dflat? Why not just leave it as C# and make things simpler.

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    On many instruments, C# and D♭ are different notes (different pitches/frequencies). Having separate musical notation for equal-tempered instruments like the piano would be more complicated rather than less.
    – user28
    Feb 18, 2018 at 19:31
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    @MatthewRead - we know that C# and Db are different pitches on some instruments. However, this fact alone will not make much difference to why we need # and b to show the same black note on a piano. So, I guess what you have stated is acceptable. And, it's only a handful of instruments.
    – Tim
    Feb 18, 2018 at 20:21
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    Every instrument except for ones with 7 white and 5 black keys is NOT a handful. Or even two footsful or a mouthful. Feb 19, 2018 at 2:51
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    @CamilleGoudeseune It is misleading to suggest that on "every instrument except for ones with 7 white keys and 5 black keys", C# and Db are different notes. Almost all commonly available mass-produced instruments in the US (at least) are designed around 12-tone equal temperament, with C# and Db representing precisely the same frequencies. 12-tone equal temperament is a near-ubiquitous standard in my experience, though it is very common for performers to intonate certain pitches differently for effect. This is a separate issue from claiming sharps and flats to be different. Feb 19, 2018 at 17:21
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    @Stinkfoot You say "not only the piano, but all keyboards and any other instrument that has discreet stops or keys for playing the notes and does not allow for bending or some device for manipulating their fixed pitches" -- on such instruments, C# and Db are typically still taken to mean the same thing when 12-tone equal temperament is being used (nearly always, in my rather limited experience). Feb 19, 2018 at 17:24

7 Answers 7


Pretty basic and simple. Each key has 7 notes, with a different letter name for each. A B C D E F G but not always starting on A!!

Let's take Gmajor G A B C D E F G - except the F needs to be F#. So far so good with your idea. Let's take Fmajor. F G A A# C D E F. Oops, there are two A notes - and no B. Try writing it out on the lines and spaces we call staves. See the problem?

EDIT: For the commenters who may have missed my reasoning - still in key F - What would you do about a key signature for that key. Possibly put a # so the A notes get changed? Oops again! Every time an A nat. was needed, it'd have to be marked. Or, no key sig. Then # each A as needed. And there'd never be a note on the middle line, treble clef. What a waste!

2nd EDIT: maybe for the folks who found the answer difficult to understand.

For simply naming the black keys on pianos, we could indeed just use sharps - or flats alone. But even that would create a dichotomy. Some would prefer sharps, some flats. The problem is actually alive and kicking on some guitar driven sites, where flats seem to have become obsolete. Any note which is not a simple letter name takes on the name of the next note down, and adds a sharp. Thus a semitone above A is A♯, that above D is D♯ and so on.

That means that a chord such as F minor gets spelled F G♯ C. Which could work. Find each 'note' on guitar (or piano, if you like), and play. Voila, an Fm chord!

Take a chord sequence, in key F major. Chord IV becomes A♯. For those with very little understanding of theory, that's not a problem. Those with more experience know immediately there's no A♯ chord (or note, even) in key F. It's called B♭ - and has been for centuries. (Unless you're German!)

So, if the original part of the answer was insufficient, stuff learned by tens of thousands of musos would be invalidated by purely using sharps (or flats).

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    Lots of upvotes on this answer, but I don't see how it explains anything. It just leaves me more confused.
    – Cypher
    Feb 20, 2018 at 19:35
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    I am not sure your answer is the problem. :) It sounds like your answer is saying, "because it would be confusing on sheet music". Is that it? And is that really the only reason?
    – Cypher
    Feb 20, 2018 at 19:49
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    @Cypher - no, it's not the only reason. But it's a very basic, simple reason. Others, such as needing # and b to show proper intervals, are important, too. It's just that that was all I wanted to show in the answer here.
    – Tim
    Feb 20, 2018 at 19:52
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    An image may make this example easier to understand.
    – Stevoisiak
    Feb 20, 2018 at 20:05
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    This is an important point: the ability to choose either sharps or flats provides a very useful notational convenience for representing certain keys that would be difficult to write if you could only use one or the other, which is entirely distinct from the differences caused by natural pitches, and seems to have been missed in the other answers. It's a shame that this answer is hard to understand (not that my theory is good enough to provide a better way of phrasing it, however), but it is worth taking the time to work out what's being described here.
    – Jules
    Feb 22, 2018 at 15:12
  1. Historically, keyboards didn't always work that way. So an A# and a Bb used to actually have different pitches. Our musical notation is older than enharmonic equivalency that you get with "well-tempered" keyboards. (https://en.wikipedia.org/wiki/Well_temperament)

  2. Just speaking as an amateur classical composer, different spellings of notes have different meanings. In classical tonal systems, if I'm in the key of D, a C# is the leading tone (leads to D and wants to resolve to it), but D-flat isn't a leading tone. And if I were writing with a less-common scale, say, like Phrygian where the leading tone comes from above rather than below, you'd want to write that leading tone as a flat to show that it wants to resolve downwards.

  3. I don't know how to play a wind instrument, but I've heard that they can actually slightly differentiate pitch by different spellings. Andreas Schiff has said different spelling-meanings should influence even how pianists articulate notes.

  4. "Normal" scales are by definition made up of (half and whole) steps using each letter once. Restricting yourself to sharps would lead to horrifically complex spelling even in some basic cases: the key of F has one flat (B-flat). Think what would happen if you had to write that Bb as an A#.

    I'm trying this at my keyboard now. Instead of F G A Bb C D E, you would have to write it in the key of E# (i.e. F-natural-- that's a white key!) so that you get each letter one time: E# (ugh) F## (i.e. double-sharp), G##, A#, B# (another white key) C##, D##.

    4B. Now you could ditch the basic principle that scales are spelled by half and whole steps: F G A A# C D E and just skip the B note. But when you skip the B line on the page, it's harder to read that as a scale. The problem is much worse for, say, singers than piano. Unlike (tuned) pianos, most humans don't have perfect pitch and have to rely on relative pitch. It's much easier to use your relative pitch to sound out a whole-step than a diminished minor third.

There may be other reasons too.

Really interesting question!

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    Your observation that notes that are enharmonic in equal temperament (such as A♯ and B♭) are not necessarily equivalent in other temperaments was my first thought, and sets your answer above the rest in my opinion.
    – Steve
    Feb 19, 2018 at 9:06
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    The equal versus other temperaments point is somewhat invalid, as I think the question is more about why all flat notes can't be eradicated in favour of only using sharps. Non - 12edo instrument players will automatically adjust the pitch to agree with the key they play in. Don't think writing an Eb instead of a D# will make much difference to the note they choose to produce, apart from which, that note needs to be written as appropriate - it wouldn't be Eb in a B major arpeggio!
    – Tim
    Feb 19, 2018 at 10:44
  • @Tim: That is especially true since a D# ideally is slightly different depending on harmonic context. Especially for choir singers, a D# in a B major chord is a little higher than in, say, an Emaj7. At least for the long held chords and assuming your conductor wants to pay attention to that … Feb 20, 2018 at 8:26
  • @ChristopherCreutzig - whilst not at al sceptical about the subtle pitch differences, I think that a choir would automatically 'compensate' to sing a note in tune - it's intuitive (or maybe intunative?), so there won't be an issue, as far as the OP's question is concerned. I'm not that convinced about the same note sung with different harmonies within the same diatonic key, though. Yes, if the next song was in, say, Eb, that would be a different pitch from D#.
    – Tim
    Feb 20, 2018 at 8:46
  • The opening gambit here suggests (in my mind) that keyboards may have needed two separate keys - one for D#, another for Eb. Somewhat misleading?
    – Tim
    Oct 15, 2018 at 11:51

When we are writing or playing a piece in a key, we are pretty much choosing a set of notes to play. Out of the 12 notes used in "Western" music, we want to mainly focus on 7. That means we are choosing not to play 5 notes.

When we are choosing not to play C natural and we want to play the black key in between C and D, we say we are playing C# instead of playing C natural. That lets us play D natural in the same key when we are playing C#.

If we want to be able to play C natural but we don't want to play D natural and we want to play the key between C and D, we call it a Db so that it's clear we will not be playing the D natural.

This also explains why we have black keys in the first place instead of just making all 12 notes be on white keys and putting them all in a line and naming them A - L or numbering them 1 - 12 or something like that. The black keys were originally alterations of the white keys. They only exist because playing every song in C major or A minor or one of the modes based on the white keys is boring. Some instruments don't even have sharps or flats built into them (e.g., diatonic harmonica, bagpipes), you either can't play them at all or you have to do weird things to play them.

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    Indeed—the point of using sharp or flat is to be able to distinguish different origins for the same destination. Feb 18, 2018 at 18:59
  • @LukeSawczak - there is more than one good reason for having them. See my answer here (and the comments there, particularly Dom's) which cites Tim and topomorto and also sources and elaborates on your idea.
    – Vector
    Feb 19, 2018 at 3:03
  • so that it's clear we will not be playing the D natural. What makes this any more clear than just using a single notation for the note? If my sheet says play C# then it's pretty clear that I am not to play D. I feel like I am missing something.
    – Cypher
    Feb 20, 2018 at 19:41
  • @Cypher I'm think more along the lines of key signatures. In a key signature, the message is generally something like, "all Cs are replaced by C#" or "all Ds are replaced by Db". If you sharpen all Cs, then generally there will be no C naturals and you are saying nothing about whether there will be any D naturals or not. And vice-versa with Db. Feb 20, 2018 at 19:46

Simplistically speaking, the concepts that the Western music notation system is based around include the following ideas:

  • There is an underlying 12-note-per-octave set of notes - the chromatic scale - from which notes will be chosen to make a diatonic scale with 7 notes in the octave.
  • Any given piece or section of music will be chiefly played using one of these diatonic scales. Because of this, there's an assumption that we need to notate 7 distinct notes.
  • We want to be able to assign each of these 7 notes a different note name (A, B, C, D, E, F, G)
  • Each horizontal position on the musical stave corresponds 1:1 to a particular note letter name.

Flats and sharps are necessary to allow every version of the diatonic scale to start at any point on the chromatic scale without repeating a note letter name, or assigning different notes in our chosen diatonic scale to the same line on the musical stave.

you might question whether some of the assumptions in the western music system are actually particularly helpful in some situations, and indeed, people do invent and use alternative notation systems.

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    you might question whether some of the assumptions in the western music system are actually particularly helpful in some situations A base 7 numerical system is extremely awkward to work with, but that's what our system uses... | Slight adjustment: alternative notation systems - not just alternative notation - alternative systems of music entirely that don't use our 7 notes, our method of calculating of intervals, etc etc - all of which are counterintuitive and persist mostly due to inertia: To change, we'd have to rip up all our books and scores and modify some of our instruments.
    – Vector
    Feb 19, 2018 at 0:19

@Tim and @topomorto focus on a very important reason for using sharps and flats: They are necessary for building/spelling scales correctly in all keys. But we also have this:

Bert Ligon - Jazz Theory Resources, Volume One, Chapter 1

(Emphasis mine)

Altered notes want to continue in the direction in which they have been altered. Sharps indicate a raised note and the direction it wants to resolve. Flats indicate a lowered note and the direction it wants to resolve.

Accidentals when written correctly, make lines easier to read. The note about C is not always C#. It may be Db under certain circumstances.

If a line moves up from C to D through a chromatic note, that note is C#, indicating the alteration and the direction of the resolution. If a line moves down from D to C through a chromatic note, that would be Db, indicating the alteration and the direction of the resolution.

(He explains in a different place - could not find the exact spot right now - that the exception is when we want to spell out a scale. For example, if we want to spell out the Eb Major scale, we write:
Eb-F-G-Ab-Bb-C-D with flats, even though we are moving upwards in terms of pitch.)

Aside from allowing us to represent scales correctly, when used properly sharps and flats will give us the most accurate representation of the music being notated.

  • Don't understand this viewpoint at all, sorry.
    – Tim
    Feb 18, 2018 at 21:18
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    In certain contexts this is true especially in chromatizim , but spelling makes a big difference. Knowing something is a 3rd vs a 4th vs a 2nd is a big help in notion it helps us recognize patters. If it was only to show directions keys with many sharps or flats would constantly have to change what they use to comply with these ideas.
    – Dom
    Feb 18, 2018 at 21:40
  • @Dom If it was only to show directions keys with many sharps or flats would constantly have to change what they use to comply with these ideas - good point. I am going to modify this answer.
    – Vector
    Feb 18, 2018 at 23:12
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    @Tim - Please explain what you do not understand. Ligon, who has excellent credentials - see: Bert Ligon - Professor of Jazz / Director of Jazz Studies, University of South Carolina (that book is used as a text in schools) explains that sharps and flats help notate the music more accurately by representing its flow in the notation. (Note that in light of Dom's comment, I edited my answer.)
    – Vector
    Feb 19, 2018 at 0:07
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    One of the few good answers on this question.
    – user43681
    Mar 1, 2018 at 20:39

At a theoretical level, D flat and C sharp are not the same note. At a practical level, depending on instrument, temperament and performance style, they might not be the same actual pitch. This could mean various things:

For a composer writing tonal music it is important to know the context of the notes you are using so that you can write appropriate harmonies, and to understand the structures you're working with so as to write music which fits with the style you're using. Thus we need to understand the differences between enharmonic equivalents because if you're composing in D major a D flat (flattened tonic) implies very, very different things to a C sharp (which is the leading note and a perfectly ordinary thing to see)

For a performer the use of sharps and flats gives us the same clues the composer was working with. As we develop in our knowledge of the theoretical ideas behind the music we're playing, we can then use those clues to help us play the music in a more understanding way. This is of especial and vital importance where the performer is expected to harmonise the written line or to improvise around it, such as in baroque music or the obvious modern example of jazz.

And they aren't even really the same pitch. Pianos compromise because it makes them feasible to build, transport and play. Violinists don't have to worry about this, as they can place their fingers anywhere they like; neither do singers. Most wind instruments allow a level of flexibility in the pitch for each fingered note and skilled players can exploit this.

Why would they do this? Because you can make the music sound better if you understand what the interval relationships are meant to be in a perfect world where nobody had to use compromised tuning systems for the sake of practicality, and can adjust their notes so that they get not just a proper D flat but exactly the right D flat for the current situation in the music. This is all based on frequency ratios, and turns into a much bigger discussion about the compromises inherent in temperaments and how you can almost never avoid them.

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    Although it's true that a note notated D flat and another notated C sharp might not be the same pitch, two different notes notated D flat might also not be the same pitch. Is the difference in pitch directly related to the difference in name? Feb 21, 2018 at 9:58
  • @topomorto within the same key I'd say yes. Between keys, no. Feb 21, 2018 at 13:45
  • @MatthewWalton I wouldn't take it for granted that even within a single key two occurences of a same-named note will have the same pitch. The simplest example is the second degree: within the dominant chord, you'd tune this to a perfect fourth below the , i.e. ratio ¾·³⁄₂ = ⁹⁄₈ from the tonic. But in the minor chord, you'd normally want the third to coincide with the subdominant, however a (Ptolemaic) minor third below the is at a ratio ⅚·⁴⁄₃ = ¹⁰⁄₉ from the tonic. (In the key of C, this gives the frequencies of 294.3 Hz resp. 290.7 Hz for the note D.) Feb 22, 2018 at 13:53
  • Whilst what you state makes sense, I wonder if a string player actually fingers C# and Db in slightly different places subject to what sounds better, or whether it just happens automatically, without the mental approach being in place telling him which to play.
    – Tim
    Feb 24, 2018 at 8:45
  • @leftaroundabout you could argue that those aren't really the same note in the same key... for some definition of key... I think you're right for really perfect intonation it's about what chord you're in, not keys. Mar 9, 2018 at 16:37

Apart from tuning systems mentioned by others, for me, the utility of appropriately using both sharps and flats is to show the function of an accidental, especially.

That is, when playing in a particular key signature, _whether_or_not_ I think of that key signature as "moving things up or down", sharp versus flat on an accidental explains to me the harmonic or melodic structure/function.

There is also the general feeling about "circle of fifths", making some black notes sometimes "flats" and sometimes "sharps". So in that particular musical heritage there is some information imparted by flats versus sharps, in terms of related keys.

Yes, it is possible to play tricks: four flats looks the same as three sharps, and so on... but it conjures up a different image and suggests different structural relationships.

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    I've fallen for that trick. Ending up playing in A instead of Ab.
    – Tim
    Feb 20, 2018 at 8:48