According to reports, Keith Richards has said that Mick Jagger isn't very musical. I suppose he would know, given that the pair have been co-writing songs for the last forty years. Despite Jagger's input on some of the Rolling Stones' biggest hits Richards says this: "I'll play whatever Mick says he feels like singing that night. I might say, 'You realise, Mick, that you've got five songs in the same key'. But this is a musical thing and Mick is not very musical."
Richards does have some words of praise for his colleague, however. "Mick is very good at being Mick", he says.