Multiples sounds at the same time.

I have a little problem with sound, both under KDE and console.
It seems that two sounds cant be played at the same time. For example, if I am 
listening MP3 and a mail arrives, I wont hear the mail sound until the MP3 
finishes.
All the sounds are going to /dev/dsp . Also I have a /dev/dsp1 but this does 
not seem to work if /dev/dsp is busy.

Any ideas or workarounds to solve this?

Thanks, Jaime.