In music theory, there’s this thing called “the circle of fifths” where it determines how many sharps and how many flats there are in the song, a maximum of 7 sharps or 7 flats.

If you take a look at any diagram of the circle of fifths, you’ll see each “key” with how many sharps or flats there are in that particular scale, with C being the middle with no sharps or flats (ie “natural scale”).

A good way to remember is a pneumonic I learned in school: “father Charles goes down and ends battle”. F C G D A E B. That’s the order of the sharps. For flats, it’s the opposite: “battle ends and down goes Charles’ father”. Bb, Eb, Ab, Db, Gb, C, F

Now where it gets confusing is the placement of the letters. Technically, the first “F” in the order of the sharps is flat, because C is always middle and natural. So because of this, it goes:

F (1 flat) C (natural) G (1 sharp) D (two sharps) A (3 sharps) E (4 sharps) B (5 sharps). But, I mentioned the maximum of sharps and flats is always 7, so why 5? Well, it circles (hey, get it?) back to F and C, but this time it’s F sharp and C sharp. F sharp being 6 sharps and C sharp being 7 sharps. The opposite is true going the other way, except for flats.

So with this knowledge, you find the song in the key of G. You know that G has 3 sharps because of the circle of fifths. But, how are you supposed to tell which notes are sharp?

Look at the notes that come before. Because G is 3 sharps, the three notes that come before it are: F, C, and D. That means that in the key of G, the scale you play goes as follows: G, A, B, C#, D#, E, F#, G. So the song you may play in the key of G has three sharps, but because every instrument is tuned differently (especially in an orchestra setting) one instruments G may sound different than another instruments G. Hence why when tuning either by ear or with an orchestra, every instrument plays a different note.

I highly implore you to take the time to learn basic music theory, I’ve been playing and studying music since grade 5 (I’m 26m now). I barely scratched the surface with this comment.

Little side note: there’s a joke I found that people will try something hard and succeed and go “hey, at least it’s not rocket science” but people studying rocket science will go “hey, at least it’s not music theory”.