Originally Posted by: shahnenhey i already have i basic understanding of music theory (i read the complete idiots guide to music theory:second edition) is it worth it to go more advanced and get the book harmony by waltor piston? i play rock and roll and i wanna b the best i can possibly be. thanks

Walter Piston's books are outstanding. I can absolutely guarantee you will learn a lot about harmony from that book. However, using that book to learn rock & roll guitar music might be like trying to kill a housefly with a tank. :)

I would start something a step above the "Idiot" book before you go to Piston. Since you have access to GT, start here with my tutorials covering a lot of this material.

Music Theory Overview
http://www.guitartricks.com/tutorial.php?input=495

Circle Of Fifths
http://www.guitartricks.com/tutorial.php?input=835

The most important thing about theory is how you apply it.

Piston's book is brilliant. However, it teaches harmony by demonstrating tonal harmonic functions by example using standard Baroque & Classical pieces. Unless you are already very familiar with the standard repertoire from Bach, Beethoven & Brahms, etc. you might be in way over your head. And it also assumes you already understand functional harmony and are ready to apply that basic understanding to musical pieces (orchestrations & piano pieces).

More to the point, it has nothing about applying music theory to playing the guitar, much less rock and roll. Since you want to play rock & roll on the guitar, you might benefit from a book that approaches theory from that perspective. For example:

http://www.amazon.com/Hal-Leonard-Fretboard-Mastery-Book/dp/0793597897

Check out my music theory tutorials. And remember, I can point you to tons of other GT tutorials that will also show you more about how to learn theory and apply it to rock guitar playing. :) Have fun with it!