#2
Pink Floyd commonly used a blues scale you can hear it in almost every glimour solo. However, Gilmour liked to toy with different notes thatmay not have been in the scale (or key) but sounded interesting. A lot of the stuff from The Wall used a dorian scale, you can hear this in Empty Spaces and the Another Brick In The Wall parts. Similar story with Radiohead, Jonny is extremely well trained in terms of theory, so he uses any scale imaginable (in other words, he just screws around with anything and makes it sound phenomenal.)
IN/ RAINBOWS
IN RAIN/BOWS
IN RAINBOW/S
IN RAINBOWS/
IN RAIN_BOWS
RA D IOHEA _D
_RAD IO HEA D
#3
the floyd is all rock and roll --- pentatonics and blues. it's HOW gilmour uses them that gets people to listen.

radiohead is a bit more open, i think, but i don't pay attention to them.
Looking for my India/Django.
#4
Pink Floyd has been basically covered. Pentatonics or blues scale with a few flavourful notes and excellent phrasing.

Radiohead however, don't tend to use any scale more than any other scale. They use a large number of different scales and the music does not always move in a linear fashion. It's difficult to talk about Radiohead because they vary greatly depending on whether you're looking at them as a guitar rock band or as a electronic band.