picking the correct key

[maxym.srpl]

I’ve noticed that some songs are written in C major, others in A♯/B♭ major, D major, E major, etc. What factors influence an artist’s or composer’s choice of key?

Watching videos, the same producer changes the key from song to song.

Let’s stick to electronic instrumental music, to avoid singer voice range issues.

With regards

[Benedict]

There is no such thing as "correct" or "more betterer" Key/Scales. Nor do Scales have a vibe per se. Ok, so an Arabian Scale will feel Egyptian more than say C Maj but that is cultural, not factual as such.

So the thing is that the composer picks a Key/Scale that suits what they are doing for one of many reasons which can range from 'C Maj is easy' to 'wanting a specific turn of phrase' that requires B Min Aug to comfortably allow that sequence of notes.

Further, you can (and should) create your own Scales for pieces. The thing about Scales is they only exist to help other musicians muck in with you as y'all pick away on yer banjos and fiddles. So if you want to make a piece with C, C# and A, you may do this. The only proviso being that you can have the relevant audience understand what you are doing - not the scale but the Story being told. You do this by helping the listener understand the context and by being consistent. Show your pattern a few times and people (who want to) will follow. People with no sense of tune are inconsistent, which is what makes them a pain to listen to (and a great joke on Idol shows).

[mjudge55]

For an instrumentalist it can be about what feels best "under the fingers" to play. Also some instruments like guitars have interesting options like open strings/harmonics that only work in expected ways in combination with certain keys in certain contexts, depending on how they're tuned. You also have synth patches and samples that sound best for the song in certain pitch ranges. Decide your highest priority parts and pick a key that's the best compromise for all of them. A DJ might think about how it will feel if a song is in Fmin and then the next song is in a completely unrelated key or the exact same one -- either could be effective for a specific "moment" in a set.

There's also just "random" picking, sometimes just for variety, to challenge yourself, to flex, to do what some tutorial mistakenly told you to, to do what your hero does. These are valid and can interact with the instrument you're on -- the instrument feels a certain way under the fingers and the patch sounds a certain way when played in a certain range and these spawn ideas that might not occur to you otherwise. So things can go in the opposite direction -- you pick a key for "dumb" reasons and it helps define the track you come up with. All is well that ends well.

[EyeCloud]

For an instrumentalist it can be about what feels best "under the fingers" to play. Also some instruments like guitars have interesting options like open strings/harmonics that only work in expected ways in combination with certain keys in certain contexts, depending on how they're tuned.

Can’t think of any better advice than this.

The only other thing I can think of is ease of playing a transposing instrument, where some keys are much easier to play in than others. The range of an instrument might also be a factor if you’re playing in the highest or lowest part of the register.

[cryophonik]

There are no hard rules or guidelines for selecting a key. It usually just comes down to what sounds right for you, but you can't disregard this:

...singer voice range issues.

The same concept can apply to a singer's range and the instrument(s) playing the melody(ies). For each, you should consider both the physical limitations of their ranges and their sweet spots. But, their range does not dictate the key, it only affects the range of the notes in the melody (which often dictates or infers the key). This is an important distinction. So, whether it's an instrument or a vocalist, there will be a range where the melody works well and it's good practice to find that sweet spot and transpose the key accordingly.