Thank you very much Peter,
you gave me the right direction for everything!
There are sound shields for incoming sound and spectrum analyzing like this one: http://bliptronics.com/item.aspx?ItemID=116
and there are sound shields for playing sounds like this one: Audio Shield for Arduino
it looks like it could work together to me, just a noob question: can i have 2 shields one one Arduino?
Thanks,
Roy.