compressor 4 is out on the app store and i was woundering seen as i got logic exspress the only thing i want that i didnt get with exspress is the compressor so i waas woundering will the compressor 4 thats aviable on the app store work with logic exspress and do the same job as the 3.5 that comes with studio? or is 4 only for video ?

thnaks
p.s a simple exsplanation of what the compressor does would be goo dto