Determining the key

I'm still very much learning theory but I think I've got some knowledge already. But one thing has always bugged me; it's not well or at all explained in what I've been reading. Any info I read on this topic has left me clueless as before. How (in practice) can you determine the key of the song. All I really need this right now is to know where to play my solo. I've got a lot of riffs but am not sure in what key the song is - in what key to play the solo.

I don't look into what chords or notes I'm playing when I construct riffs, I play whatever sounds good. For example this is a snippet off of Necrophagist's Stabwound:

Tuned to D



D||--------------------------|-----------------------------|

A||--------------------------|-----------------------------|

F||--------------------------|-----------------------------|

C||--------------------------|-----------------------------|

G||--9--6--9--6--9--6--9--6--|--7--7--7--9--7--7--10--7--|

D||--------------------------|-----------------------------|



--------------------------|---------------------------------|

--------------------------|---------------------------------|

--------------------------|---------------------------------|

--------------------------|---------------------------------|

--9--6--9--6--9--6--9--6--|--7--7--7--9--2------4----10---|

--------------------------|--------------0------2-----------|



----------------------------|-----------------------------|

----------------------------|-----------------------------|

----------------------------|-----------------------------|

----------------------------|-----------------------------|

--9--6-----6--------------|--7--------9--------10--7--|

----------7-----5--2--2--2--|-----0--0-----0--0-----------|



----------------------------|-----------------------------|

----------------------------|-----------------------------|

----------------------------|-----------------------------|

----------------------------|-----------------------------|

--9--6-----6--------------|--7--------9--------10--7--|

----------7-----5--2--2--2--|-----0--0-----0--0-----------|

And this rhythm is played when the solo starts:

|---------------------|

|---------------------|

|-------5--7----------|

|---------------------|

|-2--1--3--5----------|

|-0--3----------------|

One puzzles me here is that the rhythm is not something 'fixed'. Notes are scattered throughout the entire rhythm part. And the solo is played in A harmonic minor. How can you tell from the rhythm that the solo needs to be played in A? Or can the rhythm change to A just for the solo?


That's my first question. The second is how to determine the key in in "standard" metal song. I've read something about looking where the song revolves. If that's the case than you're pretty much stuck in E as far as metal goes? For example I have a track that goes something like this:

Tuned to D



D||----------------------------------|----------------------------------|

A||----------------------------------|----------------------------------|

F||----------------------------------|----------------------------------|

C||------------3---------------3-----|------------3---------------------|

G||------2---2---2-------2---2---2---|------2---2---2---5-2-----3-0-----|

D||--0-1---3-------3-0-1---3-------3-|--0-1---3-------3-----4-2-----2-1-|

 

----------------------------------|----------------------------------|----||

----------------------------------|----------------------------------|----||

----------------------------------|------------------------3-------3-|----||

------------3---------------3-----|------------3---------2-------2---|----||

------2---2---2-------2---2---2---|------2---2---2-----1-------1-----|----||

--0-1---3-------3-0-1---3-------3-|--0-1---3-------3-0-------0-------|----||

Now I have absolutely no idea in what key should I play the solo if the rhythm plays this part. In D? These notes actually are in D harmonic minor but notes change a lot throughout the song.

As you can see I'm pretty confused about this. I just want some info that can help me in practice. Can something like circle of fifths come in handy here or should I in these cases just play over a scale to figure out what sounds best?

The key is mostly (I think always) the chord, major or minor, with which a song ends, the last chord played. Also when a melody ends, for example, on the note D, the song is in the key of D major or D minor. One should be able to determine the key, from the scale used in the solo. It is indeed possible that the key changes during the song, a so called transpose, The chords used within a key are normally the I,ii,iii,IV,V,vii, (see chord progressions on this site) but may also include borrowed chords, altered chords, etc. The TAB above seems to be in D. Read something about keys on Wikipedia, for example, http://en.wikipedia.org/wiki/Key_%28music%29

Sorry, I mean "the Tab above seems to be in the key of D minor"

In metal mostly powerchords are used for the back up, so it doesn't really matter wether the key it's major or minor,

And this rhythm is played when the solo starts:

|---------------------|



|---------------------|



|-------5--7----------|



|---------------------|



|-2--1--3--5----------|



|-0--3----------------|

this piece is in g harmonic minor , also the solo played over it is in g harmonic , the scales change a lot in this song i think it all are harmonic minor scales that are used and the first part(intro) is in D harmonic minor

correct me if i'm wrong