Today, Alexis Petridis takes up his post as Guardian rock and pop critic. It's a more difficult job than ever: popular music now encompasses a vast range of sounds and bands, from Slipknot's nu-metal to Atomic Kitten's teeny pop and the 'new prog' of Radiohead. Here he surveys the musical landscape of 2001 - and explains how, when he was a child, he decided a life of listening was for him.