Hey Guys,
There are quite a few players out there that love to layer their guitars, one specifically, Jon Frusciante. I play acoustic mainly and if you listen to a lot of acoustic players they add maybe one or two harmonizing layers of acoustic guitar. This add a nice vibrant lushness to the song and I was wondering what the theory was in harmonizing guitar keys/chords? I'm not too familiar in this area and any info would be great. Thanks.

My Gear:
Guitars: Vintage LP, Martin DX-1, Epi Viola Bass,
Amps: Marshall JMD501
Effects: Empty Set right now
^ it depends, there are different ways to layer guitars. i would imagine john frusciante generally just layers chord inversions to fill out the sound.
Some good lessons about harmonizing guitars are here on the site. Go to the lessons header and look for harmonizing.
Other than that, harmonizing is nothing else than adding a note on top of the root. When you are in C major and you have a d as a root you can take the 3rd (minor, F) and the 5th (perfect, A). When your next note is a b you can take the 3rd (minor, D) and the 5th (flatted 4th, F) to harmonize.
You you have to look at the actual context, in which key you are and with wat intervals you want to wokr.
Different intervalls cause different sounds.
Experience with it and find a sound you like!
try relative minors, minor 3rds, and of course either a perfect 4th or 5th.

the last two lines in Sphinx1992s post are the fundamentals of harmony
Quote by King Twili
It's just me and Doris here ;_;

Quote by Zaphikh
Poops is the chat MC - but here we know him as Early Cuyler.

Free Downloads, Yo!
yeah, fruscianes a good example. totally beside the point but my brother was saying he filled up a whole either 12 or 24 channel mixer of guitar parts for one song. haha hes great..
^ thats no biggy, manson managed to use 60 some odd tracks layering guitars on one of the songs on "antichrist superstar" i love layering multiple guitars over each other. in fact my major problem has always been saying "ok thats 30 tracks, its enough"
another way to look at this..as an example..playing in thirds..scale wise...key of C ...play ionian mode and the other guitar plays the phrigian mode..

if the melody of a song or a solo is in just the notes of the key your in...this technique works fairly well and is fairly easy to execute with two players...out of key notes require some adjustment of the parts of course...but this parallel harmony...two voices going in the same direction...the fun part is when you play the parts "contra melody" style..(and not get lost in your part) in different directions..think JS Bach...or new orleans jazz.. each player having their own line...but at some point coming back "home"...

play well