I've been looking into variations on the following question: why was X piece written in Y key? For instance, why did Beethoven choose to write the Moonlight Sonata in C# minor? Presumably we can transpose a piece and, in theory anyway, it will still be the same.

I know that this question has been asked before, but I'd like to expand on the previous questions asked by other posters. In particular:

There are a number of opinions of composers about each key. C major is considered "innocent and childlike", for example, but one source refers to F-sharp minor as "A gloomy key: it tugs at passion as a dog biting a dress. Resentment and discontent are its language.". I disagree with that opinion on F-sharp minor (I find it to be a playful key in which dances "make sense").

So I suppose the question really is: how does a composer develop their particular style and thereby attribute certain desirable qualities to each key? For example, I've already chosen F-sharp minor to be a playful, dance-like key and G-sharp minor to be a slow, haunting key. That's my personal opinion, but I can't define why I hold it.

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    It's personal. Different people can perceive the exact same line many different ways. Theory tells you what something is, but it does not tell you how you should feel when you listen to it. A good composer is aware of this and will write using what they feel personally to convey their idea. It's not guaranteed everyone will view it the same way though. – Dom Oct 17 '16 at 16:01
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    Please see my answer to a very similar question in which I list all the reasons for picking a particular key. – John Wu Oct 17 '16 at 23:40
  • @NeilMeyer Absolutely! Quite a few pieces by Chopin are in C# minor. One of the possible reasons for that is that in this key, the longer fingers fit more easy on the black keys (which are further away from the wrist), while the shorter fingers (thumb, pinky) can rest on the white keys in between. Similarly for B major and E major. There's an answer with this perspective at the same question that John Wu already linked. – user18490 Oct 18 '16 at 5:28
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    I think this is pretty much a duplicate of the aforementioned question. – user18490 Oct 18 '16 at 5:29
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    Potentially. My actual question was how does a composer develop a sense of what he/she can do in a particular key, so it's slightly different – Michael Stachowsky Oct 18 '16 at 17:08

For each composer, there are different reasons, but here are some.

Ease of Playing

If you had never played the guitar before, I could probably teach you a chord progression in E minor pretty quick. If I wanted to teach you the same chord progression in E flat minor, it would be much harder. (assuming you don't have a capo!) Most instruments have keys that are easier to play in— for instance, it is easy to play in D major on a violin or cello, because many open strings are available; or on a piano it is easier to play a simple tune in C major that E flat major because you can just use the white keys.

Tone Quality

Different keys have different sounds. On string instruments, if you play in a key that has a lot of notes that could be played on open strings (for instance, D major), it will sound brighter and more resonant, because the notes will ring other strings that are the same pitch or share overtones. A key such as E flat minor does not share open strings, and so will sound darker on stringed instruments.

Perfect Pitch

Composers who have perfect pitch will often hear a melody in their head and write it down in the key they hear it in. Sure, they could transpose it later, but that might make them lose the feeling of the melody.

Hope that helps.

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    Just want to emphasize the "per instrument" aspect of the "Tone Quality" point. For instance, on a standard Bb trumpet, most notes above the staff tend sharp, but not all to the same extent, so different keys can give you a noticeably different feel to the piece. I wouldn't expect most composers to know such minutia on most instruments, but I have known it to be a factor, particularly in regards to the composer's "primary" instrument. – Tin Man Oct 18 '16 at 17:50
  • This is too simplistic an answer to be the chosen one. Many key factors come into play (no pun intended.) One very significant factor is not ease of playing on an instrument, but the instrument range itself. Operas, for example, pay heed to the vocal ranges of the male or female singers. Also, composers and orchestrators are typically very much aware of how the individual instruments sound and their quirks and minutae...it's their job. – dwoz Oct 19 '16 at 13:50

One thing to note, that was important back in Bach's time, was Piano Temperament.

Modern pianos are tuned in Equal Temperament (also known as out of tune). In 12T-ET, each of the twelve notes C-B are exactly 100 cents apart, and each key sounds the exact same, just a number of cents up or down the scale.

However, 12T-ET is a modern (20th c.) development. Bach's famous piano series, The Well Tempered Clavier, is written for a Piano tuned in Well Temperament. The cycle includes a piece in every major and minor key, and is a tour of the sounds of well temperament.

In well temperament, the fifth from C to G is not the same as the fifth from G to D. Because it's impossible to tune a piano perfectly in just harmonic tuning, different tunings came in to use. Bach just happened to be a champion of well temperament. But in these non-12T-ET tunings, different keys had a truly completely different sound.

If you haven't had the chance, look up a Well-Tempered tuning performance of the Well-Tempered Clavier. The cycle was designed for this tuning; modern Equal Temperament pianos do not do it justice.

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    Side notes: 1) we don't know the exact tuning for which Bach intended the WTK, although there has been solid research into this 2) it is still up for debate if the whole WTK really was to be played without tuning one or more times during the cycle. – 11684 Oct 18 '16 at 19:32

There are a few ways, some more concrete and others less so. The role of instrumentation is a big factor, especially in determining "heroic" characteristics with the use of brass fanfares, etc. But others are just a byproduct of prior compositional practice; if enough pieces of a certain character are written in a given key, that key acquires a given characteristic.

But of course these things aren't all-encompassing. Here is a Chopin prelude in G-sharp minor that is anything but slow and haunting!

Rita Steblin wrote a book called "A History of Key Characteristics in the 18th and Early 19th Centuries" that discusses this exact issue. A quick translation from a treatise by Christian Schubart can be found here.


In the final analysis, you choose a key because that seems like the best key to express your ideas in. You don't have to give any intellectual justification for it!

One practical issue is the relatively restricted compass of may instruments. For example if you are writing for strings, the lowest note of the viola and cello is C. If you write a piece in B, the lowest key-note those instruments can play is almost an octave higher than if you write in C. If you write in F, you can use the lowest C is the dominant of the key, but if you write in E, the lowest dominant (B) is an octave higher.

In Beethoven's early career as a composer (including the time when the "Moonlight" was written) the compass of the piano was only 5 octaves, F to F, and the limited compass was an issue for Beethoven, particularly at the top of the range. In fact some editors have "improved" what Beethoven actually wrote by going a note or two above the compass of the instruments he had to work with. Of course with the modern 88-note piano keyboard, this not usually such a big deal - though "non-standard" pianos that extend the 88-note compass in both directions have been built.


When it comes to wind instruments, there might also be the following considerations: availability of tuning and the related accuracy of pitch. For example, the most common tuning of a horn is F; less commonly you may find Bb, but this is the most common tuning of trombones. This might lead to the key Eb being used rather than E, for instance. In early days when brass instruments were not yet equipped with valves, some notes were almost not even possible to be played.


I took a class on the meaning of music and this was one of the things we discussed. On the whole, we were exploring the idea of whether music had any inherent meaning or if the commonly accepted meanings were socially constructed. It seemed in the end that this is really an opinion since many people over the years have argued both ways. I personally came to believe that music does not have inherent meaning, except for a few possible exceptions. One exception being how we refer to pitch, being high vs low. Strong, low frequencies tend to resonate through the body and can be felt through the ground, given enough amplitude. Higher pitch frequencies are more so heard than felt. So since we have ears on our head, the highest part of the body, and can feel low frequencies below that, it's easy to suggest that our convention of referring to them as low and high are related to where they stimulate us vertically. However, we could still argue that this is a social construct since the sound isn't actually propagating any differently based on how high we're able to feel it; it's really just how those sound waves are capable of interacting with our body, where high frequencies are not as able to penetrate as the low ones and are more likely to bounce off instead of vibrating our chests.

So the issue at hand when we discuss the meaning of music is that we are not able to use music to explicitly refer to an object (without the use of lyrics). For instance, we're not able to say musically, "this is a tree", or even just "tree". Music is arguably the most abstract of the arts for this reason.

Beyond that, when we approach things more abstractly, we are typically referring to these different keys as having some sort of emotional meaning and emotions are subjective. Everyone experiences happy and sad and mad and lonely differently. It is commonly accepted that Major is happy and Minor is sad but it's also easy enough to find examples of Major keys used for sad songs and Minor for happy ones. Major/Minor only gets more complicated when you add 7ths, where a Minor 7 tends to feel less sad to the average person and a Major 7 tends to feel less happy. I think that the abstract nature of music is one of the reasons that it can be so useful for expressing emotion; it allows the listener to interpret the emotional content from their own perspective without having to look past the explicit statements. However, this is also why it is entirely subjective, making it quite difficult to nail down a particular key or tonality as having a defined meaning.

There have been a lot of social constructs created over the years; far too many to cover in this answer (however long winded I tend to be). For instance, horns have been used to represent heroes quite often. This can be attributed to the use of a horn to signal the return of the soldiers from war, or the use of the horn to signal the army to attack. As others have mentioned, before valves, horns were designed for specific keys due to their limitations in producing some intervals from the fundamental frequency. So the more commonly used keys for heroes tend to be the keys that are best accommodated by the most common horns, which are generally the "flat keys" (those with flats in the key signature).

For a somewhat less academic approach to the subject, I recommend watching The Lion King and listening to the sound track. You'll find examples of instruments having a specific meaning, such as horns for the hero, strings for tension and sadness, as well as scales having a meaning, such as happy songs being Major and, one that I find particularly interesting, "exotic" tonalities/scales being used to represent the bad guy, like harmonic minor (I find this particularly interesting because this construct seems to be based on such scales having a foreign sound, which can be used to represent bad things, most likely due to xenophobia; it's also often used to represent the "evil seductress" but I don't think there is one in The Lion King).

So I'd say that the meanings that composers have for certain keys are based on social constructs. Some of these are based on the instruments themselves, others on cultural aspects, and some of it is just based on the idea that we are using an abstract medium to convey an abstract experience (emotion), so people tend to feel something when they write and happen to choose a given key at the time. There's a lot of content out there if you're looking to study this more academically but I can't remember any particular book or paper that I could suggest off hand, unfortunately.


There is no single right answer to this question, and many of the ones already posted are insightful and correct. However, one thing has not yet been mentioned: synesthesia (or chromestesia). In relation to music, this is when you associate specific notes with specific colors. A composer endowed with synesthesia (e.g. Alexander Scriabin) might want to express a certain musical passage in a certain color, meaning that they would want to write it in a certain key. For instance, a musical piece evoking feelings of nature might be written in a key that the composer associates with the color green. With feelings of love, it might be dark red.

It is important to note that these color associations are individual and are usually not shared in the exact same way by other people with synesthetic tendencies. It only serves to explain why a composer would choose a certain key: because its sound would simply make sense in describing whatever it is that they wish to describe with a particular piece.

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    I might add that synesthesia is not incredibly common, so it's unlikely that it has been the source of most composers' descriptions of specific keys. Some are known to actually see a scene with their synesthesia, perhaps a landscape, and there are also other synesthesia experiences, such as tasting sound, though that appears to be less common from what I've heard. Synesthesia is basically a crossing of senses, so you could hear a smell or taste a sound or see a taste, etc. – Basstickler Oct 18 '16 at 13:57

Synesthesia can be between other senses and even sound to sound. Some people (a very few; not me) perceive certain notes as having a unique sound (timbre). So F# would have the same unique timbre in all octaves. They uniquely identify the note by this sound. Is that different from identifying notes by pitch? I don't know. I think it's just a variation on perfect pitch or perhaps just one way of trying to describe perfect pitch.

I do recall a rock guitarist saying that D minor is the most minor sounding of all the minor keys. Maybe that's an "instrument/tuning specific thing". Would a significant number of rock guitarist agree? Probably not.

Several people with perfect pitch have told me that they can't stand to listen to music in anything but the original key. I think that's an expectations alignment thing.

My high school music teacher told a story of how he got a speeding ticket after the national speed limit was reduced to 65MPH. All the music in his head while driving had been in the key of the frequency of the car driving at 65MPH for so long that he just couldn't drive 55. I doubt that the story was original ;-)

  • Original story - Johnny Dankworth used it to defend his speeding accusation. Still got fined! – Tim Oct 19 '16 at 13:55

don't know how scientific this is but it's believed each key really has subtle differences in moods. Some even go as far as believing that pieces sound much better in certain key(s) than in other key(s).

as far as transposition goes, it's not destroying the integrity of the piece. You just might have to work harder on interpretation.


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