I have started using Logic Pro 9, and I'm using a Behringer Xenyx 302USB mixer. I'm having a problem when it comes to the piano roll. I can preview the samples and such but when it comes to laying down the actual track, I can't hear the samples, or the outcome at all. I have a simple set up so i don't think it's the mixer. I tried figuring it out myself and looked online to find an answer but I didn't. Help?