Need Help!

Ok, I have 2 questions:

1. How can you tell what key a song is in? (i.e. what note and if it's major or minor)

2. If I have written a song containing the chords G,B,E, would I improvise a solo by using a scale that contains those notes (despite having other notes in it) or improvise using several scales, such as G pentatonic and B pentatonic and E pentatonic?

Please Help

usualy u can tell what key a song is in is it will tell you..if not i think its the first chord or the most used chord that tells you the key..i dont know about the second question, use you ears to solo over it..if u think it sounds good stay with it..i know nothin bout theory..i let my ears make the decision if it sounds right

Most questions of this type have been thoroughly and comprehensively covered in old threads. Search in the "Theory" section, if that is possible. Noticingthemistake is pretty much the resident guru of theory, so check his comments out carefully. But there are lots of other people here who know their stuff too.

But yes, the key of a song is usually the chord that it begins and ends with, though there are exceptions. A chord is made up of notes--usually three.

Well this was most likely answered in the theory forum somewhere, but I believe I can do a pretty good job of answering your question. Yes the previous replies did point you in the right direction. If the song starts on a G major the odds are good that the song is in G major. But the way the chords work with the other chords is an excellent beacon. In a major progression, the chord flavors (we'll leave it at as a matter of major vs. minor) will foloow a pattern. In a major progression the I chord (the chord that is the key of the song) will be major. The ii chord is minor. iii is minor. IV is major. V is major. vi is minor and vii is diminished. Heres an example. If your progression starts on a G major. You could play a B minor but not a B major if you want your progression in G. So if that helps im glad. But if that didnt work, I have one last piece of advice. If you decide it's in G major. Your lead should be in G major. The seven notes you would play in G major are G A B C D E F#. But the major pattern is not as easy for beginners to make leads as the pentatonic. So then what pentatonic could you play? Heres a great revelation. If a song is in a major key. Find the sixth note. In G the sixth note is E. Then play in the minor scale of that note. E minor is the same as G major. It is the same seven notes. And the pentatonic is 5 notes but they all fit. So play in E minor pentatonic in this case and have fun :)

As said above u can find the key by looking at the first cord which is often the first degree.It works most of the times but u can also be helped, if u got the part, by the signature at the beginning.I f u have one #, it's the key of G major, 2 # u're in D major... 6 # u're in f# major( it's easy to remember it's a fifth progression: G,D,A,E,B, F#).U could have more #, but generally u'll have b at the signature, it's easier to write. Same stuff: 1 b = F maj, 2 b = Bb maj.....6 b = Gb maj it's a forth progression : F,Bb,Eb,Ab,Db,Gb). But there are also what's is called the relative scales G maj and E min contains the same notes. If u wanna go further notice that the G maj notes can also belong to A Dorian, B phrygian, C lydian.....
By using what is above, u can use for the melody the notes from any the scales using the G maj notes but also the G maj pentatonic scale, why not G min pentatonic scale if u wanna sound bluesy or if u wanna sound a bit weird: g maj harmonic or melodic scales...the possibilities are infinite...just listen and enjoy.