Be all technical for me, will you?

This, right, is driving me insane.

Heres the thing – I have lots of artists on my iTunes library that simply dont show up on my iPod.

An example:
– There are three albums or collections worth of Otis Redding.
– However, should I suddenly want to listen to him, if I flick to artists, several other artists beginning with O show up in the list, Otis: No.
– And no, he doesnt show up under R for Redding, either.
– None of his albums show up in the albums list on the iPod
– He shows up nowhere in the Genres. Nowhere at all.
– But the songs are all present in the song list, and he pops up all the time on shuffle.

SO
The only way I can listen to him is find every song I want to listen to is to find each one, individually, in a long alphabetical list of songs. Which is kind of annoying when you have a memory like mine and can remember vague lines from songs (and even then mainly with doodoodoo where most of the words should be) but not the official names.

This happens with several artists and I cannot for the life of me work out why. Does anyone know? Has anyone EVER come across this before?