k is there anyway to determine a key without just knowing or looking at the sheet music?

2nd question can u only use certain scale with certain key's??

Every scale (major, harmonic minor, etc) can be played for each key, A, B, C, etc.

And as you grow better at theory, you can easily figure out the key through various methods, fitting it around a chord, fitting it into scales, and by ear.
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the key of the the song is pretty much the scale. of course, you can use modified scales, like harmonic minor, pentatonic, and so on.

and i don't really understood what you meant with the first question. check my sig for some key signature trainers.

and don't double post dude
1. looking to see what notes your playing on guitar like C D Eb F G Ab Bb C would be C minor

2. no like if your playing a chord progresson in E you could also play a C# scale because thats the minor key of E
Quote by nath1142
if i'm right the key is determined from what scale/scales u use right>?

key is determind by the notes like however many sharps or flats you have just look at the circle of fiths......the circle of fiths is the key to life