LogicAudio and MIDI

[Pirateking]

Hi

I am running an old Korg keyboard through a MIDI/USB interface into Logic Pro 6, trying to use the keyboard to play the MIDI instruments. I know nothing about MIDI. Everything seems to be working; the lights on the interface show data is flowing through it, and the numbers in the bottom-right hand corner of Logic show that it is reading the signal coming in. However, I cannot hear any sounds being produced through the headphones. There is probably some really obvious Logic setting change I need to make to have the sound come out correctly, but the Logic manual is totally useless. Any thoughts?

[Pirateking]

Sorry, I didn't see the MIDI beginners thread on this board. That has already cleared up some stuff.