I know how to see if say, 4 chords are in the same key, but how do you know what key it is? Say you had 4 simple power chords, F#, G, A, and D. How would you know what key that's in and why? Thanks.

Like, would it be in the key of F#?

You need to know if the chords are major or minor. Then you just find a key in which they fit.
In Cmajor, chords are:
C, Dm, Em, F, G, Am, B.
This same pattern applies to all major keys (i.e. all major keys have M,m,m,M,M,m,M chords (M=major, m=minor)).
For a minor key, you use the same chords, but start two "scale-notes" down, so A minor uses same chords as C major.

I'm tired, so this probably doesn'ät make any sense

__________________

remember, in Cmajor (or Aminor), the B is half diminished, or min7b5 (minor seventh flat fifth)

ok, sulution49, using your example:
(" - " means minor)


if the tonic is F#- = F#- / G / A / D (phrigian mode, applies to the Dmajor key)

if the tonic is A - = F#-7b5 / G / A- / D (dorian mode, applies to the Gmajor key) this example doesn't apply exactly to your example, 'cause you have said the chords are power chords, notate that the first one is b5


etc....

to know the keys (of sharps), you have to go by fifths:

C (A-)= no alterations (all notes natural, C, D, E, F, G, A, B, and with that you make the chords. example: C / E / G= C major chord, A / C / E= A minor chord)

G (E-)= 1 alteration: F# (G, A, B, C, D, E, F#)

D (B-)= 2 alterations: F# / C# (D, E, F#, G, A, B, C#)

A (F#-)= 3 Alterations: F# / C# / G# (A, B, C#, D, E, F#, G#)

ETC.....

and the flat ones(you have to go by 4ths):


C (A-)= no alterations

F (D-)= 1 alteration: Bb (F, G, A, Bb, C, D, E)

Bb (G-)= 2 alterations: Bb / Eb (Bb, C, D, Eb, F, G, A)


etc.......

note: here's a trick to know fast the key without thinking "this fucking song has 5 flats........ then what fucking scale has 5 flats????"...... you gonna lose your mind

if the keys is in sharps, look at the last one: add it 1/2 step and it's your key....
obviously, if doesn't have alterations, is Cmajor

example: you have 4 sharps, the last one is (must be) a D#, then you are in E major...


if the key is in flats, look at the one before the last: that tells you the key....

example: you have 5 flats, the one before the last is (must be) a Db, then your key is Db....

i hope this helps you....

my fingers hurts!!!!

__________________