I've recently become obsessed with Les Miserables and Miss Saigon. The music has inspired me tenfold to compose, write similar music.

I've posted on here before on how to compose, and I'm trying my best but struggling with something:

When you denote the time signature, you also have to say what key it is in, right? For example: A Minor etc... but how do you know what key it is in exactly? It is the first note you play; does that become the key it is in?

I know what I want it to sound like. I have a vision in my head, but I wouldn't (at this stage) know what 'key' it is in.

I am a beginner, but very determined and would appreciate some help.

  • 11
    I think the close vote as 'too broad' is a bit mean here... from a beginner point of view, this is a reasonable question, and an answer doesn't need to be over-long to give the right impression. Commented Jan 3, 2017 at 14:51
  • @topomorto thank you! It is a genuine one. Without Tim's answer I would have felt an injustice to the music world to start writing without the knowledge of time sigs, and keys etc... It is nice to know it's not considered bad practice to just start composing (or trying to at least).
    – cmp
    Commented Jan 3, 2017 at 14:55
  • 1
    Related: music.stackexchange.com/questions/15221/…
    – Kevin
    Commented Jan 3, 2017 at 16:20
  • It might not even be in a key, in which case just write down whatever makes it easiest to read.
    – OrangeDog
    Commented Jan 4, 2017 at 14:06
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    @TransverseAudio - I've run out of pinches of salt to take with that sort of information! All they missed were the fairies at the bottom of their garden.
    – Tim
    Commented May 3, 2020 at 7:40

5 Answers 5


The key is very much where the song feels like it's at rest; at home. It's more likely to show itself in the last chord, which, aftre all, in most songs, is where it finishes, safely back home.

The key you write it in, though, could be any of the 12 majors or 12 minors. If it's sung, that key should be one in which your voice sounds good - not too high or too low, with a little strain if the song warrents it. However, someone else could easily be unhappy in that key, and need to change to suit their voice. Some songs need to be in a particular key for the chords to sound authentic on guitar as a special case, but that's another story.

When writing a song ( I mean 'writing' as in making it up), the key doesn't have to be a paramount consideration. Nor does the time sig. That comes into importance when the song needs to be written DOWN. Sometimes, you might even write a song, and not be aware of its time sig. until then. Doesn't matter. You're too busy being creative!

If it's a song going through your head, it's either major or minor. Establish that first, then play a chord. Any chord, and go from there. When you have the whole thing done, look at the chord pool you've used, and relate that to the key. For example, if there's mostly G, D and A, it'll probably be in D major. D=I, G=IV and A=V, with the D giving the most stable feel to which it will come to rest on.

  • 4
    Thanks @Tim. I guess that's what I'm struggling with. Is it perfectly 'normal' then to write a song and not take into account its key or how many beats in a bar etc... Or is this considered bad practice? Is it safe to do this at the end?
    – cmp
    Commented Jan 3, 2017 at 13:46
  • 5
    Absolutely fine! That part is what I would term the 'academic' part, and if one's not carefil, can get in the way of creativity, and actually spoil the songwriting. Maybe if the middle 8 or whatever has to wait for another day, it's worth reflecting on key/time sigs at that point.
    – Tim
    Commented Jan 3, 2017 at 13:53
  • The OP didn't say he wanted to write a vocal song (yeah, he didn't say he didn't , either :-) ). Selecting a key for instruments or instrument ensembles does make a difference due to the natural ranges and resonances of the instruments. You also left out the fact that there are 3 common minors, and a bunch of other modes as well. Commented Jan 3, 2017 at 14:14
  • @CarlWitthoft there are various identifiably different minor tonalities and scales, but that fact doesn't generate multiple versions of minor keys. Commented Jan 3, 2017 at 14:25
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    @CarlWitthoft - I was taken to task some time ago for confusing minor scales for different minor keys! Not falling for that again! Most modes fall into maj. or min. The OP is a beginner at this - hence the question- so I kept it basic.
    – Tim
    Commented Jan 3, 2017 at 16:44

You might or might not have a key in mind when you start to write a song. Reasons you might have a key in mind when you start to write:

  • You are writing a piece of music to fit in a sequence with another piece of music (e.g. you want them to work in continuation in a DJ mix or something)
  • You know that a certain singer prefers certain keys
  • You are writing for an instrument that only plays in a certain key.

Each of those cases generates its own answer to "How do I know what key to write in?".

As Tim says, it's probably more common, though, to write a piece first and only later, possibly need to think about what key it's in (and even then, as he also says, only if you need to notate it in standard notation or analyse it for some other reason).

In this answer, I said " The way music theory is commonly taught tends to mix up genuine music fundamentals, culture-specific terminology and notation, and style-specific musical advice into one big pot". This is one of those cases, I think!

When we say that a piece is 'in A minor', all it means is that:

  • The tonal centre is 'A', for some part of the piece
  • The tonality of the piece corresponds somewhat (though not necessarily completely) with the natural minor scale.

You might think that "some part of the piece" and "corresponds somewhat" sounds very uncertain and wishy-washy. And you'd be right! The reality is that although a piece called (say) Passacaglia and Fugue in C minor seems very proud of its key, prominently declaring it in the title, 'key' is not a fundamental musical concept - it simply relates to a particular practicality of writing down or describing a piece in a certain way.


Here’s a lesson aimed at singers that is also applicable for composers and arrangers:

The primary concern for key selection is matching the range and tessitura of your vocalist or soloist. Typically this depends both on the overall range, and the ranges where the heaviest or most difficult passages lie. Most passages should lie solidly within chest voice or head voice and not ride the passagio in between. Professional singers will be more comfortable with using both registers; casual singers may only know how to use chest voice. This will affect both the key and overall range of your melodies. There are similar concerns, but different ranges, for solo instruments like guitar, violin, or clarinet.

The secondary concern is making the music readable and comfortable for your accompanists. Jazz musicians and wind bands tend to like flat keys (F, B♭, E♭, A♭ major). String ensembles lean toward sharp keys (G, D, A major). Guitarists prefer a few specific keys depending on exactly how they tune (mostly sharp keys but not D major unless you tune down). Pianists are idiosyncratic but sometimes prefer more neutral keys (C, F, B♭, G, D major) for ease of reading and play. These rules of thumb are partly based on the instruments’ ranges and partly on the complexity of reading and fingering accidentals (which is different for transposing instruments like woodwinds and horns).

  • So to make a simple advice for the OP, he should initially write the piece in C major or A minor because this will mean no sharps or flats in the key sgnature. Then after he has finished, he can use his composing software to transform the entire piece to desired range for the target performers.
    – awe
    Commented Jan 6, 2017 at 9:25
  • If his “composing software” is his own voice and a piano or guitar, that might not work out so great. Most folks in my experience use their voices and preferred instruments to improvise and work out the melodies, harmonies, and rhythm. Commented Jan 6, 2017 at 18:13

In addition to the great answers here, I did want to point out one time where key does matter. Not every key sounds the same, so composers will often gravitate towards a particular key to get a particular feel. For nearly every modern instrument, the pitches are chosen according to what is called "equal temperament." This set of pitches let an instrument play in any key, but it turns out that you can't always get it quite perfect. Some keys will naturally have ever so slightly different harmonics than others. These different harmonics add colors to the music that a skilled composer can take advantage of.

The most evident of these appears in any music with a piano. One of the things you want when you tune any instrument is for each note to be twice the frequency of the note one octave below it. However, in practice, real pianos have a slightly inharmonic behavior. The first overtone of a piano is not quite exactly double its fundamental frequency. Accordingly, one tends to stretch the octaves to get them to sound right. This stretching effect causes pianos to have slightly different sounds in different keys, because the ratios between the notes are not quite a perfect logarithmic scale.

Over time, composers learn that certain keys lend themselves to particular feelings that they wish to bring forth. Once they have their opinions, they can often pick a key to compose in based on the feeling they want, rather than having to hunt for the correct key.

As for what a key "is," it's an artifact of what humans have generally found to sound good. Remember, our ears were not designed to listen to music. They were designed to listen to the environment, letting us know where water is or where predators might be. Much of that hardware is still present in our modern day ear, and it leads us to like certain sounds and dislike others. What we have found is that the ear likes some concept of a "root" frequency and the harmonies are built around that note. From there, we find that many cultures have their opinions of what should happen within those harmonies. Classical Western music, for example, has a very clear set of chord progressions that are favored above others because it resonates with what the listener expects (culturally, and with respect to the hardware between our ears).

That being said, these concepts are pliable. Never assume your key or chord progression must be set in stone. Compare classical with modern music and you'll find that modern music contains many more discordant sounds. The modern mind appreciates that discord more than the mind of a 1700's noble did, so naturally the sound has become more populated with them. Modern music still has a concept of a key, but it is more willing to explore what happens when you leave that key behind.


If you are a beginner, you are likely writing for a single instrument or voice. Write in a key in which the range of the piece will fit comfortably into the range of that instrument (or voice). Highest note? Lowest? Then, if you have further choice, find a key the fits the instrument. Comfortably "under the hand" for piano, for example, or the equivalent for some other instrument.

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