how to synch your external hdd

well,
ive got the following 'problem", where i need your help:
ive got a external hdd, where i got some music on etc...
is there any possibility to synch my pc with this external hdd?
e.g. if i got some new music on the hdd, i dont wanna search the whole hdd for those 2 titles or copy the whole folders on my pc...

i hope you got my point and can give me some advices :)

cheers