Damned annoying isn't it? It has to do with terms of copyright. In most cases of recorded music used in this way, there is no legal obligation to say who the recording is by, so long as the royalties are paid. In some cases, where people have specifically stipulated, the recording can only be used by permission, then the music is credited. I thinks that's right, I'm sure someone will tell me if I'm wrong.

TTFN M'Lady P.