Volume decreases between songs

> Can someone help me with a very frustrating problem
> please. I notice that when I am playing a list of songs
> saved on my Hard Drive the volume decreases after one
> song plays so that the next song is almost inaudible,
> this dosen't happen after every song everytime but it
> happens quite often. This Happens whether i am using
> windows media player or winamp. when I go to the volume
> controls in control panel the "Wave" slider is far below
> where I left it.
> Any Ideas as to why this happens? And How can I fix it?
> Someone please respond