What is it that defines what key a song is in???

Question

I dont fully understand what makes a song a particular key

Answer 1

The key signature.
It's the combination of sharps or flats at the beginning of the line in written music.

Answer 2

the key signature at the beginning of the song tells you what key you're in basically. you have to determine if the song is major or minor either by ear (minor sounds a little sad while major sounds upbeat).
another way to tell if its minor vs major is to look for a lowered third. if the key signature had no sharps or flats it would either be C major or a minor. if there were virtually no e flats it's most likely C major.
another way (or so i'm told) is to look at the last note of the piece. it's usually the first note of whatever key the song is in

Answer 3

The key signature on the written piece determines the key.

Answer 4

well the notes that are played in it make it a key, sounds like you dont know a lot about music, maybe read up on wikipedia or something.

bcuz music is written down, right and the sounds or notes you put it in (by writing it down in a specific way) determine the key.

Answer 5

MOST SONGS ARE DETERMINED BY THE SINGER. IF HE SINGS FLAT THEN THE SONG WILL BE FLAT AND IF SHARP THEN SHARP. THEN A THROUGH G