How do I find out what key I'm in?

[Eggman]

Is there a rule of the thumb kind of way to find out what key one is playing in??

[Chickwithapick]

I think it's basically the first chord you play in a song. Like, if a song has a progression of G, D, C, then I think you're in the key of G. Can anyone tell me if that's how it works for sure? I know absolutely nothing about theory, but I think someone told me that once.

[Philphool]

Sometimes it's not so easy to tell the key, but usually the key is likely to be the chord that the song ENDS on rather than begins on. (although it is often the case that the song begins AND ends on the chord named for the key)
The reason is that in western music, we like the song to RESOLVE to the tonic chord, so most songs are written that way. Is this absolutely necessary? No, but that's what usually is done.

[suppaenitetere]

To tell what key you're in you need to know your scales inside and out. You also need to know which chords go for which note in the scale, for example the I is always major II always minor IV major and V major.

Another thing you need to realize is that there is a point you reach in theory that says "You can only play this set of notes for this chords, except you can really play whatever sounds good to you." Dont limit yourself to following the key if you can make it sound good doing something else. Many songs have a chord that doesnt fit or on a solo they will use pieces of different scales or chromatic licks.

I think i've rambled, that probably made no sense. To answer your question shortly whatever the tension is released to. When you feel the musical tension release then chances are its the tonic chord.

[KrYpT]

one of my trick is :

i listen to the song and try to play some kind of solo using major or pentatonic scale then when i find its seem to fit correctly i take the root of the scale and it give me an idea in which key the song is play

not sure if its correct but it help me a lot :)

if you want to be sure and you know how to read music without tab you can find the key by looking at the firts bar of the song

[Eggman]

I know how to read music but the problem is that most of the time I dont use sheet music (I couldnt even play guitar with sheet music, but I can play alittle piano)..

The scale trick is offcourse a good idea... thanks..

Eggman

[Hannu]

But i read that the key can change many times through the song...
?!?!?!?!?!?!?

[The Fury]

But i read that the key can change many times through the song...

If your reading from a sheet of music - standard notation, then the key change will be marked with a new Key Signature.

[Angelhearts]

I just use whatever sounds like it fits. I don't know anything about modes, scales (other than the most common ones). You just have to explore and use what sounds good. Thats my advice although it probably isn't that much help. Play along with CDs and stuff, it does work.