Okay, this isn't completely correct but it's the closest I've come to figuring out the chords for the song. Just try it, trust me it's extremely close the key is just a little different. What I mean is the key in the verse is a tad higher, and the chorus is a bit lower than the original, but that isn't much of a problem when playing the song. This will hold you over until someone (maybe me :)) is able to figure out the true chords Tegan and Sara play. Capo 2 G2: play a Bm on the 7th fret D2: play an F#m on the 7th fret Intro: D A F#m G Em G Build a wall of books between us in our bed Em G Repeat, repeat the words that I know we both said Em G Relax into the need we get so comfortable Em G Remember when I was so strange and likable D A G D A F#m G I Just want back in your head D A G D A F#m G I just want back in your head D A G D A F#m G I'm not unfaithful but I'll stray G2 D2 When I get a little scared G2 When I get a little scared D2 When I get a little ( Tab from: http://www.guitartabs.cc/tabs/t/tegan_and_sara/back_in_your_head_crd_ver_2.html ) Em G When I jerk away from holding hands with you Em G I know these habits hurt important parts of you Em G Remember when how sweet and unexplainable Em G Nothing like this person unlovable D A G D A F#m G I Just want back in your head D A G D A F#m G I just want back in your head D A G D A F#m G I'm not unfaithful but I'll stray G2 D2 When I get a little scared G2 When I get a little scared D2 When I get a little scared When I get a little G2 D G Run run run D2 Run G2 D G Run run run D2 Run D A F#m G I Just want back in your head D A G D A F#m G I just want back in your head D A G I'm not unfaithful but I'll stray D A G I'm not unfaithful but I'll stray D A G I'm not unfaithful but I'll stray D A F#m G I'm not unfaithful but I'll stray There you have it! I know, the key change is a bummer but these chords are phonetically the most accurate I've found, and I've been searching around for a while. Rate this if you think it's not complete rubbish!
Source: http://www.guitartabs.cc/tabs/t/tegan_and_sara/back_in_your_head_crd_ver_2.html