Radiohead - Optimistic
Drop D Tuning
Low To High - D A D G B E

Riff I: (slide to all these chords)
e |---------------------0---0---0--0--0---0---0---0--0--0---0---------|
b |---------------------x---x---x--x--x---x---x---x--x--x---x---------|
g |--14-14---14-16--16--11--11--11-11-11--10--10--10-12-12--11--------|
d |--15-15---15-17--17--12--12--12-12-12--12--12--12-14-14--12--------|
a |--15-15---15-17--17--12--12--12-12-12--13--13--13-15-15--12--------|
D |--0--0----0--0---0---0---0---0--0--0---0---0---0--0--0---0---------|

Riff II:
e |-------------------------------------------------------------------|
b |-------------------------------------------------------------------|
g |------7-7-7--5-5-5-5-5-5------9-9-9--5-5-5-5-5-5-------------------|
d |------x-x-x--x-x-x-x-x-x------x-x-x--x-x-x-x-x-x-------------------|
a |------5-5-5--3-3-3-3-3-3------7-7-7--3-3-3-3-3-3-------------------|
D |--0-0-0-0-0--0-0-0-0-0-0--0-0-0-0-0--0-0-0-0-0-0-------------------|

Riff III:
e |----------------------------2-2--2-2-2-2-2-------------------------|
b |----------------------------3-3--3-3-3-3-3-------------------------|
g |--5-5-5--4-4-4-4-4--3-3-3---2-2--2-2-2-2-2-------------------------|
d |--x-x-x--x-x-x-x-x--x-x-x---0-0--0-0-0-0-0-------------------------|
a |--3-3-3--2-2-2-2-2--1-1-1---0-0--0-0-0-0-0-------------------------|
D |--0-0-0--0-0-0-0-0--0-0-0---0-0--0-0-0-0-0-------------------------|

Riff IV: (this is the part where it's mostly just percussive strums 
          done very quickly)
         (here's where I think the chords are)
e |-------------------------------------------------------------------|
b |---3--3---3--3--------3-3-3-3--------------------------------------|
g |---2--0---3--2--------0-0-0-2--------------------------------------|
d |---0--0---0--0--------0-0-0-0--------------------------------------|
a |-------------------------------------------------------------------|
D |-------------------------------------------------------------------|